Pneumatic tire

Abstract

The invention provides a pneumatic tire capable of improving uneven wear resistance and dry road grip performance. A pneumatic tire (1) includes a first profile (P1) extending from a tire equator (C) toward a first tread end (T1). The first contour (P1) includes a first arc (11), a second arc (12), and a third arc (13). The radius of curvature TR2 of the second arc is 30%-40% of the radius of curvature TR1 of the first arc, and the radius of curvature TR3 of the third arc (13) is 25%-40% of the radius of curvature TR2 of the second arc. A second connection point (15) where the second arc and the third arc are connected is located further toward the tire axial inner side than the first tread end (T1). The separation distance (La) between the second connection point and the tire equator (C) in the axial direction of the tire is 30%-34% of the cross-sectional width of the tire. The third arc (13) extends further outward in the tire axial direction than the first tread end.

Description

Technical Field

[0001] The present invention relates to pneumatic tires. Background Art

[0002] Patent Document 1 below describes a pneumatic tire in which the outer surface of the tread portion in the tire meridian section is determined. The tire includes a crown arc across the tire equator, an intermediate arc connected to the crown arc, and a shoulder arc connected to the intermediate arc. Moreover, the first curvature radius TR1 of the crown arc, the second curvature radius TR2 of the intermediate arc, and the third curvature radius TR3 of the shoulder arc are TR1>TR2>TR3. Such a tire can effectively suppress uneven wear of the tread portion.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-14312

[0004] For example, when the tire is driven at the limit on a circular track, a load index exceeding 100% may be applied to the tire. In such driving conditions, depending on the profile of the tread portion, the ground contact pressure may be locally high in the area near the tread end, which may cause partial wear in the above area and reduce the side resistance. Summary of the invention

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

[0006] The present invention relates to a pneumatic tire, comprising a tread portion, wherein, in a meridian section of the tire in a normal state, the tread portion includes a first profile extending from the tire equator to a first tread end side, the first profile includes a first arc extending from the tire equator to the tire axially outward, a second arc connected to the first arc and extending to the tire axially outward, a third arc connected to the second arc and extending to the tire axially outward, 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 are respectively The tire has a single curvature radius, the curvature radius TR2 of the second arc is 30% to 40% of the curvature radius TR1 of the first arc, the curvature radius TR3 of the third arc is 25% to 40% of the curvature radius TR2 of the second arc, the second connection point is located at a position axially inner than the first tread end, the axial separation distance between the second connection point and the tire equator is 30% to 34% of the cross-sectional width of the tire, and the third arc extends to a position axially outer than the first tread end.

[0007] The pneumatic tire of the present invention can improve uneven wear resistance and dry road grip performance by adopting the above-mentioned structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a tire meridian cross-sectional view showing one embodiment of a pneumatic tire of the present invention.

[0009] Figure 2 Yes means Figure 1 A diagram of the profile of a tire in a tire meridian section.

[0010] Figure 3 yes Figure 1 An expanded view of the tread portion of a tire.

[0011] Figure 4 yes Figure 1 An enlarged view of the second transverse groove.

[0012] Figure 5 (A) is a plan view showing the shape of the contact surface of the tread portion of Example 1, Figure 5 (B) is a plan view showing the shape of the ground contact surface of the tread portion of Comparative Example 1.

[0013] Description of reference numerals:

[0014] 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 section width. DETAILED DESCRIPTION

[0015] Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. In order to help understand the present invention, the accompanying drawings include exaggerated representations and representations that are different from the actual structure in terms of dimensional ratio. In addition, when there are multiple embodiments, the same or common elements are marked with the same reference numerals throughout the specification, and repeated descriptions are omitted.

[0016] Figure 1 This is a tire meridian cross-sectional view of the pneumatic tire (hereinafter sometimes referred to as "tire") 1 of the present embodiment, including the tire rotation axis (illustration omitted) in a normal state. The present invention is suitable for use, for example, in passenger car tires that can be used for competitive driving on a circular track. Since such a tire 1 travels at a relatively high speed, a load with a load index exceeding 100% is sometimes applied during driving. The above-mentioned "load index" in this specification refers to the maximum mass allowed to be loaded on the tire under specified conditions specified under the JATMA specifications, that is, an index expressing the maximum load capacity as an index. However, the tire 1 of the present invention is not limited to a tire that can be used for such competitive driving.

[0017] The above-mentioned "normal state" refers to a state where the tire 1 is assembled on a normal rim (not shown) and adjusted to a normal internal pressure and is unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in the normal state.

[0018] The “regular rim” is a rim that has the specifications specified for each tire in the specification system including the specifications to which the tire 1 conforms, such as “standard rim” in JATMA, “design rim” in TRA, and “measuring rim” in ETRTO.

[0019] The “normal internal pressure” is the air pressure specified for each tire in the specification system including the specification to which the tire 1 is based, and is the “maximum air pressure” for JATMA, the maximum value recorded in the table “TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES” for TRA, and “INFLATION PRESSURE” for ETRTO.

[0020] like Figure 1 As shown, the tire 1 has a tread portion 2. The tire 1 also has a pair of sidewall portions 3 connected to both sides of the tread portion 2 in the tire axial direction.

[0021] Figure 2 2 is a diagram showing the profile of the tread portion 2 of this embodiment. The above profile in this specification is the contour 1a obtained by filling the recessed portions provided on the surface of the tire 1 in the tire meridian cross section in a normal state. The above recessed portions include the circumferential grooves and transverse grooves described later. Figure 2 As shown, the tread portion 2 includes a first profile P1 extending from the tire equator C to 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 from the tire equator C to the tire axially outward. The second arc 12 is connected to the first arc 11 and extends to the tire axially outward. The third arc 13 is connected to the second arc 12 and extends to the tire axially outward. The second connection point 15 is a point where the second arc 12 is connected to the third arc 13. The second connection point 15 is located at a position closer to the tire axial inner side than the first tread end T1.

[0022] The first arc 11, the second arc 12, and the third arc 13 have single curvature radii TR1, TR2, and TR3, respectively. In addition, the curvature radius TR2 of the second arc 12 is 30% to 40% of the curvature radius TR1 of the first arc 11. Furthermore, the curvature radius TR3 of the third arc 13 is 25% to 40% of the curvature radius TR2 of the second arc 12.

[0023] In addition, the tire axial separation distance La between the second connection point 15 and the tire equator C is equal to the cross-sectional width Wt of the tire 1 ( Figure 1 The third arc 13 is 30% to 34% of the tire tread (as shown). Furthermore, the third arc 13 extends to a position axially further outward from the first tread end T1. Such a first profile P1 can make the third arc 13 smoothly contact the ground outside the first tread end T1 under driving conditions where the load index exceeds 100%, thereby expanding the contact area. Such an expansion of the contact area can suppress the increase in local contact pressure near the first tread end T1, and suppress the uneven wear and reduction in lateral resistance near the first tread end T1. Therefore, the tire 1 of the present invention has excellent uneven wear resistance and dry road grip performance. The section width Wt is the maximum width of the tire 1 in the axial direction of the tire 1 excluding the rim guard (not shown), the pattern or text on the side of the tire, etc.

[0024] In order to effectively exert the above-mentioned effects, the curvature radius TR2 of the second arc 12 is preferably 32% or more, and preferably 38% or less of the curvature radius TR1 of the first arc 11. In addition, the curvature radius TR3 of the third arc 13 is preferably 27% or more, and preferably 38% or less of the curvature radius TR2 of the second arc 12. Furthermore, the tire axial separation distance La between the second connection point 15 and the tire equator C is preferably 31% or more, and preferably 33% or less of the cross-sectional width Wt.

[0025] The first tread end T1 and the second tread end T2 described later are defined as the contact positions at both ends of the tire axial direction when the tire 1 in the normal state is loaded with a normal load and contacts the flat surface at a camber angle of 0 degrees (hereinafter referred to as the "normal load loading state"). The length of the tire axial direction between the first tread end T1 and the second tread end T2 is the tread width TW (e.g. Figure 3 shown).

[0026] In the case of pneumatic tires with various specifications, the "normal load" is the load specified for each tire in the specification system including the specifications to which the tire is based, and is "maximum load capacity" in the case of JATMA, the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLDINFLATION PRESSURES" in the case of TRA, and "LOAD CAPACITY" in the case of ETRTO. In other words, the first tread end T1 and the second tread end T2 can be said to be the two ends of the tire axial direction where the tread portion 2 is in contact with the plane when the tire is running with a load index of 100%.

[0027] 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 a point where the first arc 11 is connected to the second arc 12. The outer arc 16 is connected to the third arc 13 and extends axially outward from the tire. In the present embodiment, the outer arc 16 is an area where it is not expected to touch the ground even in a situation where the load index exceeds 100%, such as competitive driving on a circular track. The third connection point 17 is a point where the outer arc 16 is connected to the third arc 13. In addition, the first connection point 14, the second connection point 15, and the third connection point 17 are points where the radius of curvature on both sides of the tire axial direction changes.

[0028] The axial separation distance Lb between the outer end 13e (same as the third connection point 17) of the third arc 13 and the tire equator C is preferably 44% or more of the section width Wt, more preferably 45% or more, preferably 48% or less, more preferably 47% or less. Since the separation distance Lb is 44% or more and 48% or less of the section width Wt, even in a driving condition where the load index exceeds 100%, the third arc 13 is in contact with the ground and the outer arc 16 is not in contact with the ground, thereby suppressing a local increase in the ground pressure.

[0029] The tread portion 2 includes a second tread end T2 located on the opposite side to the first tread end T1. In the normal tire meridian section, the tread portion 2 includes a second profile P2 extending from the tire equator C to the second tread end T2 side. Moreover, the second profile P2 is in a line-symmetric relationship with the first profile P1 with the tire equator C as the axis of symmetry. Even with such a second profile P2, under the driving condition where the load index exceeds 100%, the third arc 13 can be smoothly grounded on the outer side of the second tread end T2 to expand the ground contact area. Therefore, the tire 1 of this embodiment has better uneven wear resistance and dry road grip performance. Among them, the second profile P2 is not limited to being in a line-symmetric relationship with the first profile P1.

[0030] The curvature radius TR1 of the first arc 11 is preferably 600 mm or more, more preferably 700 mm or more, preferably 1200 mm or less, more preferably 1100 mm or less. Since the curvature radius TR1 is 600 mm or more and 1200 mm or less, the ground pressure can be made uniform from the first arc 11 to the third arc 13. The curvature radius TR4 of the outer arc 16 is not particularly limited, but is preferably 15 mm or more, more preferably 20 mm or more, preferably 45 mm or less, more preferably 40 mm or less.

[0031] The tread portion 2 of the present embodiment is designated with respect to the direction in which it is to be installed on the vehicle. The first tread end T1 is the inner tread end located on the inner side of the vehicle when installed on the vehicle in the present embodiment. In addition, the second tread end T2 is the outer tread end located on the outer side of the vehicle when installed on the vehicle in the present embodiment. In the present specification, the tread portion 2 from the tire equator C to the first tread end T1 side is the inner tread portion 2A, and the tread portion 2 from the tire equator C to the second tread end T2 side is the outer tread portion 2B. Usually, when turning, a greater lateral force is applied to the outer tread portion 2B than to the inner tread portion 2A.

[0032] Figure 3 2 is a top view after the tread portion 2 is unfolded. Figure 3 As shown, 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 include a first circumferential groove 21 located closest to the first tread end T1.

[0033] The first circumferential groove 21 is arranged at the same position as the second arc 12 (such as Figure 2 In addition, Figure 2 As shown in FIG. 1 , the axial separation distance Lc between the outer edge 21e of the first circumferential groove 21 and the second connection point 15 in the tire axial direction is preferably 10 mm or more. In this way, since the second connection point 15, where the ground contact pressure may be high, is separated from the first circumferential groove 21, it is possible to suppress the occurrence of uneven wear near the first circumferential groove 21. If the separation distance Lc is too large, the formation area of ​​the third arc 13 in the tire axial direction may become smaller. Therefore, the separation distance Lc is more preferably 15 mm or more, preferably 30 mm or less, and more preferably 25 mm or less.

[0034] like Figure 3 As shown, all of the plurality of circumferential grooves 20 are located closer to the first tread end T1 side (inner tread end side) than the tire equator C. In other words, all of the plurality of circumferential grooves 20 are arranged on the inner tread portion 2A. Thus, since the rigidity of the outer tread portion 2B in the tire axial direction is maintained higher than the rigidity of the inner tread portion 2A in the tire axial direction, the ground contact pressure of the inner tread portion 2A and the outer tread portion 2B is equalized, and the dry road grip performance during cornering can be improved.

[0035] In the present embodiment, the plurality of circumferential grooves 20 include a second circumferential groove 22 located closer to the tire equator C than the first circumferential groove 21. The plurality of circumferential grooves 20 of the present embodiment are composed of the first circumferential groove 21 and the second circumferential groove 22. The plurality of circumferential grooves 20 may include, for example, other circumferential grooves (not shown).

[0036] For example, the first circumferential groove 21 and the second circumferential groove 22 extend linearly in parallel with the tire circumferential direction. The angle θ1 of the groove width center line 21s of the first circumferential groove 21 relative to the tire circumferential direction and the angle θ2 of the groove width center line 22s of the second circumferential groove 22 relative to the tire circumferential direction are preferably 5 degrees or less, and in the present embodiment, extend at 0 degrees.

[0037] The groove width W1 of the first circumferential groove 21 and the groove width W2 of the second circumferential groove 22 are preferably 4% or more of the tread width TW, more preferably 6% or more, and preferably 14% or less, more preferably 12% or less. Figure 1 The groove depth D2 of the first circumferential groove 20 and the second circumferential groove 22 is preferably 3 mm or more, more preferably 4 mm or more, preferably 8 mm or less, and more preferably 7 mm or less. Such a circumferential groove 20 suppresses excessive reduction in rigidity of the tread portion 2 and improves drainage performance.

[0038] In the present embodiment, the tread portion 2 includes a first land portion 24 divided by the first circumferential groove 21 and the first tread end T1, and a second land portion 25 divided by the second circumferential groove 22 and the second tread end T2. In addition, the tread portion 2 includes a third land portion 26 divided by the first circumferential groove 21 and the second circumferential groove 22, for example.

[0039] 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.

[0040] Although not particularly limited, the tire axial width Wa of the first land portion 24 is preferably 5% or more of the tread width TW, more preferably 10% or more, preferably less than 25%, and more preferably 20% or less. The tire axial width Wb of the second land portion 25 is preferably 40% or more of the tread width TW, more preferably 45% or more, preferably 60% or less, and more preferably 55% or less. The tire axial width Wc of the third land portion 26 is preferably more than 5% of the tread width TW, more preferably 10% or more, preferably 25% or less, and more preferably 20% or less.

[0041] In the present embodiment, the first land portion 24 is provided with a plurality of first lateral grooves 31 arranged at a first pitch length P11 in the tire circumferential direction. In addition, for example, the second land portion 25 is provided with a plurality of second lateral grooves 32 arranged at a second pitch length P12 in the tire circumferential direction. Moreover, the second pitch length P12 is preferably greater than the first pitch length P11. Thus, since the rigidity of the second land portion 25 arranged in the outer tread portion 2B in the tire circumferential direction is maintained higher than the rigidity of the first land portion 24 arranged in the inner tread portion 2A in the tire circumferential direction, the ground contact pressure of the first land portion 24 and the second land portion 25 is equalized. Therefore, the uneven wear resistance and dry road grip performance are improved.

[0042] The first lateral groove 31 and the second lateral groove 32 extend parallel to the tire axial direction. The angle θ3 of the groove width center line 31s of the first lateral groove 31 and the angle θ4 of the groove width center line 32s of the second lateral groove 32 relative to the tire axial direction are preferably 5 degrees or less, and in the present embodiment, extend at 0 degrees.

[0043] The plurality of first lateral grooves 31 each include an axially inner end 31i that is closed in the first land portion 24 without being connected to the first circumferential groove 21, and is connected to the first tread end T1. Such first lateral grooves 31 prevent the rigidity of the first land portion 24 from being excessively reduced, and improve drainage performance.

[0044] The groove width W3 of the first lateral groove 31 is preferably 45% or more, more preferably 50% or more, and preferably 65% ​​or less, more preferably 60% or less of the groove width W1 of the first circumferential groove 21. Figure 1 The first lateral groove 31 is preferably 80% or more, more preferably 90% or more, preferably 120% or less, more preferably 110% or less of the groove depth D1 of the first circumferential groove 21. The first lateral groove 31 improves drainage performance and dry road grip performance in a balanced manner.

[0045] The axial separation distance Ld between the inner end 31i of the first lateral groove 31 and the outer edge 21e of the first circumferential groove 21 is preferably 35% or more, more preferably 40% or more, and preferably 55% or less, more preferably 50% or less of the axial width Wa of the first land portion 24. Thus, the above-mentioned effect can be effectively exerted.

[0046] Each of the plurality of second lateral grooves 32 includes an axially inner end 32i that is closed in the second land portion 25 without being connected to the second circumferential groove 22. Such second lateral grooves 32 suppress a decrease in the lateral rigidity of the second land portion 25. Each of the plurality of second lateral grooves 32 includes an axially outer end 32e that is closed in the second land portion 25 without being connected to the second tread end T2.

[0047] Figure 4 yes Figure 3 A simplified enlarged view of the second transverse groove 32. Figure 4 As shown in FIG. 1 , when the tread is viewed from above, the groove edge 35 of each of the plurality of second lateral grooves 32 includes: an inner arc portion 35a extending in an arc shape on the inner end 32i side, and an outer arc portion 35b extending in an arc shape on the outer end 32e side. Each groove edge 35 has each inner arc portion 35a and outer arc portion 35b separately in the tire circumferential direction. In addition, the groove edge 35 includes a pair of axial portions 35c connecting the inner arc portion 35a and the outer arc portion 35b, a first circumferential portion 35d connecting each inner arc portion 35a and extending in the tire circumferential direction, and a second circumferential portion 35e connecting each outer arc portion 35b and extending in the tire circumferential direction. The axial portion 35c and each circumferential portion 35d, 35e extend in a straight line. In the present specification, the groove edge 35 extending linearly includes, of course, a case where the radius of curvature is infinite (∞) when the tread is viewed from above, and also includes an arc with a radius of curvature of 400 mm or more.

[0048] The outer arc portion 35b is arranged in an area (on the second tread end T2 side) where a large lateral force acts when turning. Therefore, the curvature radius TR7 of the outer arc portion 35b is preferably larger than the curvature radius TR6 of the inner arc portion 35a. Figure 3 The rigidity of the second tread end T2 side of the outer arc portion 35a is maintained high, so the uneven wear resistance is improved. Although not particularly limited, the curvature radius TR7 of the outer arc portion 35b is preferably 110% or more of the curvature radius TR6 of the inner arc portion 35a, more preferably 120% or more, preferably 300% or less, and more preferably 200% or less.

[0049] The groove width W4 of the second lateral groove 32 is preferably equal to the groove width W2 of the second circumferential groove 22 (e.g. Figure 3 55% or more, more preferably 60% or more, preferably 75% or less, more preferably 70% or less. In addition, the groove depth D4 (as shown in FIG. Figure 1 As shown in the figure, it is preferably 80% or more of the groove depth D2 of the second circumferential groove 22, more preferably 90% or more, preferably 120% or less, more preferably 110% or less.

[0050] like Figure 3As shown in FIG. 1 , the axial separation distance Le between the inner end 32i of the second lateral groove 32 and the second circumferential groove 22 is greater than the axial separation distance Lf between the outer end 32e of the second lateral groove 32 and the second tread end T2. As a result, the rigidity of the second land portion 25 near the inner end 32i is maintained to be greater than the rigidity of the second land portion 25 near the outer end 32e, and 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 preferably 10% or more of the axial width Wb of the second land portion 25, more preferably 12% or more, preferably 20% or less, and more preferably 18% or less. The separation distance Lf is preferably 4% or more of the axial width Wb of the second land portion 25, more preferably 6% or more, preferably 12% or less, and more preferably 10% or less.

[0051] The third land portion 26 is provided with a plurality of third lateral grooves 33 arranged at a third pitch length P13 in the tire circumferential direction. The third pitch length P13 is preferably smaller than the second pitch length P12. Thus, since the rigidity of the second land portion 25 arranged in the outer tread portion 2B in the tire circumferential direction is maintained higher than the rigidity of the third land portion 26 arranged in the inner tread portion 2A in the tire circumferential direction, the ground contact pressure of the second land portion 25 and the third land portion 26 is equalized. Therefore, the uneven wear resistance and dry road grip performance are improved. The third pitch length P13 is, for example, the same as the first pitch length P11.

[0052] Each of the plurality of third lateral grooves 33 includes an inner end 33i in the tire axial direction that is closed in the third land portion 26 without being connected to the second circumferential groove 22, and is connected to the first circumferential groove 21. In addition, the groove width W5 of the third lateral groove 33 increases continuously toward the first circumferential groove 21 side, for example. Such third lateral grooves 33 can easily discharge water in the third lateral grooves 33 to the first circumferential groove 21, and can suppress an excessive decrease in the rigidity of the third land portion 26.

[0053] The axial separation distance Lg between the inner end 33i of the third lateral groove 33 and the second circumferential groove 22 is preferably 50% or more, more preferably 55% or more, preferably 70% or less, and more preferably 65% ​​or less of the axial width Wc of the third land portion 26. Since the separation distance Lg is 50% or more and 70% or less of the axial width Wc of the third land portion 26, the drainage performance and the dry road grip performance can be improved in a balanced manner. The ratio Lg / Wc of the separation distance Lg to the axial width Wc of the third land portion 26 is greater than the ratio Ld / Wa of the separation distance Ld to the axial width Wa of the first land portion 24.

[0054] like Figure 1As shown, the groove depth D5 of the third lateral groove 33 is preferably 80% or more, more preferably 90% or more, and preferably 120% or less, more preferably 110% or less of the groove depth D1 of the first circumferential groove 21. Thus, high drainage performance can be achieved.

[0055] As mentioned above, although the particularly preferred embodiment of the present invention has been described in detail, the present invention is not limited to the illustrated embodiment, and can be implemented in various modified forms.

[0056] Example

[0057] Based on the specifications in Table 1, a prototype with Figure 1 The basic structure and Figure 3 The basic pattern of the pneumatic tires was tested for dry road grip performance, uneven wear resistance, and drainage performance. The main common items are as follows.

[0058] Tire size: 215 / 45R17

[0059] Air pressure: 220kPa

[0060] Rim: 17×7.5J

[0061] <Dry road grip performance, uneven wear resistance and drainage performance>

[0062] Each test tire was mounted on all wheels of the following vehicle and was driven on a circular course on a dry asphalt pavement and a circular course on a wet asphalt pavement. During the driving, a load such that the load index exceeded 100% was applied to the tire. For dry road grip performance, the ease of driving on a circular course on a dry asphalt pavement was evaluated by the test driver's senses. For uneven wear resistance, the state of uneven wear after driving on a circular course on a dry asphalt pavement was evaluated by the test driver's senses. For drainage performance, the ease of driving on a circular course on a wet asphalt pavement was evaluated by the test driver's senses. In any test, the results are expressed as a score with Comparative Example 1 set to 100 points. The larger the value, the better.

[0063] Vehicle: 2400cc rear-wheel drive passenger car

[0064] 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.

[0065] For the table,

[0066] "A" refers to a configuration in which two circumferential grooves are arranged on the inner tread portion.

[0067] “B” refers to a configuration 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.

[0068] "C" means the third transverse groove is Figure 3 form.

[0069] "D" means a configuration in which the third lateral groove is connected to the second circumferential groove and is not connected to the first circumferential groove.

[0070] The test results are shown in Tables 1 and 2.

[0071] Table 1

[0072]

[0073] Table 2

[0074]

[0075] The test results show that the dry road grip performance and uneven wear resistance of the tire of the embodiment are improved compared with the tire of the comparative example. In addition, the ground contact pressure of the contact surface 2s1 of the smooth tire having the profile of the embodiment 1 is shown in FIG. Figure 5 In (A), the ground contact pressure of the contact surface 2s2 of the smooth tire having the profile of Comparative Example 1 is shown in Figure 5 In (B). Figure 5 In (A) and (B), the areas with higher ground pressure are represented by darker colors. Figure 5 As shown in (A) and (B), compared with the profile of Comparative Example 1, the profile of Example 1 has a relatively uniform ground contact pressure.

[0076] [Note]

[0077] The present invention includes the following aspects.

[0078] [Present invention 1]

[0079] A pneumatic tire having a tread portion, wherein:

[0080] In the normal state, in the tire meridian cross section, the tread portion includes a first profile extending from the tire equator toward a first tread end side.

[0081] The first profile includes a first arc extending from the tire equator to the outside of the tire axial direction, a second arc connected to the first arc and extending to the outside of the tire axial direction, a third arc connected to the second arc and extending to the outside of the tire axial direction, and a second connection point where the second arc and the third arc are connected.

[0082] The first arc, the second arc, and the third arc each have a single radius of curvature.

[0083] The curvature radius TR2 of the second arc is 30% to 40% of the curvature radius TR1 of the first arc.

[0084] The curvature radius TR3 of the third arc is 25% to 40% of the curvature radius TR2 of the second arc.

[0085] The second connection point is located further inward in the tire axial direction than the first tread end.

[0086] The axial distance between the second connection point and the tire equator is 30% to 34% of the tire cross-sectional width.

[0087] The third arc extends axially outward from the first tread end.

[0088] [Present invention 2]

[0089] In the pneumatic tire according to the first aspect of the present invention,

[0090] The distance between the outer end of the third arc in the tire axial direction and the tire equator in the tire axial direction is 44% to 48% of the cross-sectional width.

[0091] [Present invention 3]

[0092] In the pneumatic tire according to the first or second aspect of the present invention,

[0093] The curvature radius TR1 of the first arc is 600 to 1200 mm.

[0094] [Present invention 4]

[0095] In the pneumatic tire according to any one of Inventions 1 to 3,

[0096] The tread portion includes a second tread end located at a position opposite to the first tread end.

[0097] In the normal state, in the tire meridian cross section, the tread portion includes a second profile extending from the tire equator toward the second tread end side.

[0098] The second profile is line-symmetrical with the first profile about the tire equator as an axis of symmetry.

[0099] [Present invention 5]

[0100] In the pneumatic tire according to any one of Inventions 1 to 4,

[0101] The tread portion is designated with respect to the direction in which it is to be installed on the vehicle.

[0102] The first tread end is an inner tread end located on the inner side of the vehicle when the tread is mounted on the vehicle.

[0103] [Present invention 6]

[0104] In the pneumatic tire according to any one of Inventions 1 to 5,

[0105] The tread portion is provided with a plurality of circumferential grooves extending in the circumferential direction of the tire.

[0106] The plurality of circumferential grooves include a first circumferential groove located closest to the first tread end side.

[0107] The first circumferential groove is arranged at a position overlapping with the second arc.

[0108] The distance between the outer edge of the first circumferential groove in the tire axial direction and the second connection point in the tire axial direction is 10 mm or more.

[0109] [Present invention 7]

[0110] In the pneumatic tire according to the sixth aspect of the present invention,

[0111] All of the plurality of circumferential grooves are located closer to the first tread end side than the tire equator.

[0112] [Present invention 8]

[0113] In the pneumatic tire according to the sixth or seventh aspect of the present invention,

[0114] The plurality of circumferential grooves include a second circumferential groove located closer to the tire equator than the first circumferential groove.

[0115] The tread portion includes a second tread end located at a position 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.

[0116] The first land portion is provided with a plurality of first lateral grooves arranged at a first pitch length in the tire circumferential direction.

[0117] The second land portion is provided with a plurality of second lateral grooves arranged at a second pitch length in the tire circumferential direction.

[0118] The second pitch length is greater than the first pitch length.

[0119] [Present invention 9]

[0120] In the pneumatic tire according to the eighth aspect of the present invention,

[0121] Each of the plurality of first lateral grooves includes an inner end in the tire axial direction that is closed in the first land portion without being connected to the first circumferential groove, and is connected to the first tread end.

[0122] [Present invention 10]

[0123] In the pneumatic tire according to the eighth or ninth aspect of the present invention,

[0124] Each of the plurality of second lateral grooves includes an inner end in the tire axial direction that is closed within the second land portion without being connected to the second circumferential groove.

[0125] [Present invention 11]

[0126] In the pneumatic tire according to the tenth aspect of the present invention,

[0127] Each of the plurality of second lateral grooves includes an axially outer end that is not connected to the second tread end and is closed within the second land portion.

[0128] [Present invention 12]

[0129] In the pneumatic tire according to the present invention 11,

[0130] When the tread is viewed in a plan view, the groove edge of each of the plurality of second lateral grooves includes an inner arc portion extending in an arc shape at the inner end side and an outer arc portion extending in an arc shape at the outer end side.

[0131] [Present invention 13]

[0132] In the pneumatic tire according to the twelfth aspect of the present invention,

[0133] The curvature radius of the outer arc portion is greater than the curvature radius of the inner arc portion.

[0134] [Present invention 14]

[0135] In the pneumatic tire according to any one of Inventions 8 to 13,

[0136] The tread portion includes a third land portion divided by the first circumferential groove and the second circumferential groove.

[0137] The third land portion is provided with a plurality of third lateral grooves arranged at a third pitch length in the tire circumferential direction.

[0138] The third pitch length is smaller than the second pitch length.

[0139] [Present invention 15]

[0140] In the pneumatic tire according to the present invention 14,

[0141] Each of the plurality of third lateral grooves includes an inner end in the tire axial direction that is closed in the third land portion without being connected to the second circumferential groove, and is connected to the first circumferential groove.

Claims

1. A pneumatic tire having a tread portion, wherein: In a normal tire meridian cross section, the tread portion includes a first profile extending from the tire equator toward a 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 curvature radius TR2 of the second arc is 30% to 40% of the curvature radius TR1 of the first arc. The curvature radius TR3 of the third arc is 25% to 40% of the curvature radius TR2 of the second arc. The second connection point is located further inward in the tire axial direction than the first tread end. The axial distance between the second connection point and the tire equator is 30% to 34% of the tire cross-sectional width. The third arc extends toward the outer side in the tire axial direction relative to the first tread end.

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

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

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

5. The pneumatic tire according to claim 1, wherein: The tread portion is designated with respect to a direction in which it is to be installed on a vehicle. The first tread end is an inner tread end located on the inner side of the vehicle when the tread is mounted on the vehicle.

6. The pneumatic tire according to any one of claims 1 to 5, wherein: The tread portion is provided with a plurality of circumferential grooves extending in the circumferential direction of the tire. The plurality of circumferential grooves include 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 distance between the outer edge of the first circumferential groove in the tire axial direction and the second connection point in the tire axial direction is 10 mm or more.

7. The pneumatic tire according to claim 6, wherein: All of the plurality of circumferential grooves are located closer to the first tread end side than the tire equator.

8. The pneumatic tire according to claim 6, wherein: The plurality of circumferential grooves include a second circumferential groove located closer to the tire equator than the first circumferential groove. The tread portion includes a second tread end located at a position 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. The first land portion is provided with a plurality of first lateral grooves arranged at a first pitch length in the tire circumferential direction. The second land portion is provided with a plurality of second lateral grooves arranged at a second pitch length in the tire circumferential direction. The second pitch length is greater than the first pitch length.

9. The pneumatic tire according to claim 8, wherein: Each of the plurality of first lateral grooves includes an inner end in the tire axial direction that is closed in the first land portion without being connected to the first circumferential groove, and is connected to the first tread end.

10. The pneumatic tire according to claim 8, wherein: Each of the plurality of second lateral grooves includes an inner end in the tire axial direction that is closed within the second land portion without being connected to the second circumferential groove.

11. The pneumatic tire according to claim 10, wherein: Each of the plurality of second lateral grooves includes an outer end in the tire axial direction that is not connected to the second tread end and is closed within the second land portion.

12. The pneumatic tire according to claim 11, wherein: When the tread is viewed in a plan view, the groove edge of each of the plurality of second lateral grooves includes an inner arc portion extending in an arc shape on the inner end side and an outer arc portion extending in an arc shape on the outer end side.

13. The pneumatic tire according to claim 12, wherein: The curvature radius of the outer arc portion is greater than the curvature radius of the inner arc portion.

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

15. The pneumatic tire according to claim 14, wherein: Each of the plurality of third lateral grooves includes an inner end in the tire axial direction that is closed in the third land portion without being connected to the second circumferential groove, and is connected to the first circumferential groove.

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