Pneumatic tires

Abstract

The present invention provides a pneumatic tire that ensures wet performance and improves handling stability during high-speed cornering. The pneumatic tire has a tread portion (2). The tire has ground contact ends, namely, a first ground contact end (T1), a second ground contact end (T2), and a third ground contact end (T3), when the tire is assembled relative to a regular rim at a regular internal pressure and loaded with 100%, 75%, and 50% of the regular load and ground contact with a flat surface at a camber angle of 0°. A main groove (3) and a shoulder area (5) are provided in the tread half area (2h). At least one first inclined groove (6) is provided in the shoulder area (5). The first inclined groove (6) extends in a manner that intersects at least the first ground contact end (T1), the second ground contact end (T2), and the third ground contact end (T3). The depth of the first inclined groove (6) at the first ground contact end (T1) is smaller than the depth of the first inclined groove (6) at the second ground contact end (T2) and the third ground contact end (T3).

Description

Technical Field

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

[0002] Patent Document 1 below proposes a tire that can be driven on roads and is also suitable for sports driving on a circuit track, etc. The tire of Patent Document 1 can exert excellent grip even when the ground contact pressure acting on the tread is small by defining pattern elements of the tread portion.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-51863

[0004] As vehicles become more advanced in performance, tires suitable for sports driving such as those described above seek to improve handling stability during high-speed cornering, but also need to ensure wet performance during road driving. Summary of the invention

[0005] The present invention has been made in view of the above-mentioned actual situation, and a main object of the present invention is to provide a pneumatic tire that ensures wet performance and improves steering stability during high-speed cornering.

[0006] The present invention is an inflatable tire with a tread portion, comprising: a first grounding end, a second grounding end and a third grounding end when the tire is assembled with a regular rim at a regular internal pressure and loaded with 100%, 75% and 50% of the regular load and grounded with a flat surface at a camber angle of 0°, wherein the second grounding end is located at a position closer to the inside of the tire axial direction than the first grounding end, the third grounding end is located at a position closer to the inside of the tire axial direction than the second grounding end and is located on both sides of the tire equator, and the tire equator of the tread portion and one of the first grounding ends are located at a position closer to the inside of the tire axial direction than the second grounding end. 1 ground contact end, a main groove extending continuously in the tire circumferential direction between the third ground contact end and the tire equator, and a shoulder area divided between the main groove and the first ground contact end, at least one first inclined groove inclined relative to the tire axial direction is provided in the shoulder area, the first inclined groove extends in a manner of crossing at least the first ground contact end, the second ground contact end and the third ground contact end, and the depth of the first inclined groove at the first ground contact end is smaller than the depth of the first inclined groove at the second ground contact end and the third ground contact end.

[0007] Preferably, in the tire of the present invention, the tread portion includes: the two main grooves disposed so as to sandwich the tire equator; a crown region defined between the two main grooves; and the two shoulder regions disposed so as to sandwich the crown region.

[0008] In the tire of the present invention, preferably, a tire rotation direction is specified, and the first inclined groove is inclined toward a side opposite to the tire rotation direction as it goes toward an axially outer side of the tire.

[0009] In the tire of the present invention, preferably, the first inclined groove includes an outer portion intersecting the first ground contact edge and a main portion intersecting the second ground contact edge and the third ground contact edge and having a greater depth than the outer portion.

[0010] In the tire of the present invention, preferably, an angle of the first inclined groove at the third contact edge relative to the tire axial direction is greater than an angle of the first inclined groove at the first contact edge relative to the tire axial direction.

[0011] Preferably, in the tire of the present invention, at least one second inclined groove inclined relative to the tire axial direction is provided in the shoulder region, and the second inclined groove intersects the second ground contact end and the third ground contact end and does not intersect the first ground contact end.

[0012] In the tire of the present invention, preferably, the second inclined groove includes a first portion intersecting the third ground contact end, and a depth of the first portion decreases toward the inner side in the tire axial direction.

[0013] In the tire of the present invention, preferably, the second inclined groove includes a second portion intersecting the second ground contact end, and the second portion has a constant depth in a longitudinal direction of the second inclined groove.

[0014] In the tire of the present invention, preferably, the length of the second inclined groove in the tire axial direction is 40% to 60% of the length of the first inclined groove in the tire axial direction.

[0015] The pneumatic tire of the present invention can improve the handling stability during high-speed cornering while ensuring wet performance by adopting the above-mentioned structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a development view of the tread portion of the tire according to one embodiment of the present invention.

[0017] Figure 2 yes Figure 1 Magnified view of the shoulder area of ​​the tire.

[0018] Figure 3 yes Figure 2 Enlarged views of the first inclined groove, the second inclined groove and the third inclined groove.

[0019] Figure 4 yes Figure 2 AA line section view.

[0020] Figure 5 yes Figure 2 BB line cross-sectional view.

[0021] Figure 6 yes Figure 1 An enlarged view of the land portion of the tire crown.

[0022] Description of Reference Numerals

[0023] 2...tread portion; 2h...half tread area; 3...main groove; 5...shoulder area; 6...first inclined groove; T1...first ground contact end; T2...second ground contact end; T3...third ground contact end. DETAILED DESCRIPTION

[0024] Hereinafter, one embodiment of the present invention will be described based on the drawings.

[0025] Figure 1 The tread portion 2 of a pneumatic tire 1 (hereinafter, sometimes simply referred to as "tire 1") according to one embodiment of the present invention is shown in an expanded view. The tire 1 of this embodiment is, for example, a pneumatic tire for a passenger car, and is particularly a high-performance tire that can be driven on roads and is also suitable for sports driving on a circuit track or the like.

[0026] The tire 1 of the present embodiment includes, for example, a directional pattern that specifies a rotation direction R. The rotation direction R is indicated on the sidewall portion (not shown) by, for example, characters or symbols.

[0027] The tread portion 2 includes a first ground contact edge T1, a second ground contact edge T2, and a third ground contact edge T3. The first ground contact edge T1 is the ground contact edge when the tire is assembled on a regular rim and filled with a regular internal pressure and is loaded with 100% of the regular load and contacts the flat surface at a camber angle of 0°.

[0028] In the case of tires with various specifications, a "regular rim" is a rim that specifies the specifications for each tire in the specification system that includes the specifications that the tire is based on, such as "standard rim" in JATMA, "design rim" in TRA, and "measuring rim" in ETRTO. In the case of tires without various specifications, a "regular rim" refers to a standard rim that can fully demonstrate the performance corresponding to the purpose of use of the tire.

[0029] In the case of tires with various specifications, the "normal internal pressure" is the air pressure specified for each tire in the specification system including the specifications to which the tire is based. In the case of JATMA, it is the "maximum air pressure", in the case of TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is "INFLATION PRESSURE". In the case of tires without various specifications, the "normal internal pressure" refers to the standard internal pressure that can fully exert the performance corresponding to the purpose of use of the tire.

[0030] In the case of pneumatic tires with various specifications, the "normal load" is the load specified for each specification for each tire in the specification system including the specifications to which the tire is based. In the case of JATMA, it is the "maximum load capacity", in the case of TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is "LOAD CAPACITY". In addition, in the case of tires with various specifications, the "normal load" refers to the load acting on a tire in the standard installation state of the tire. The above-mentioned "standard installation state" refers to a state in which the tire is installed on a standard vehicle corresponding to the purpose of use of the tire, and the vehicle is stationary on a flat road surface in a state in which the vehicle can travel.

[0031] The second contact end T2 is the contact end when 75% of the normal load is applied to the tire in the normal state and the tire contacts the flat surface at a camber angle of 0°. Similarly, the third contact end T3 is the contact end when 50% of the normal load is applied to the tire in the normal state and the tire contacts the flat surface at a camber angle of 0°.

[0032] The second ground contact end T2 is located axially inward of the first ground contact end T1. The third ground contact end T3 is located axially inward of the second ground contact end T2 and on both sides of the tire equator.

[0033] A plurality of main grooves 3 extending continuously in the tire circumferential direction are provided in the tread portion 2. In the present embodiment, one main groove 3 is provided between the third ground contact end T3 on one side and the tire equator C, and one main groove 3 is provided between the third ground contact end T3 on the other side and the tire equator C. The main groove 3 extends in a straight line parallel to the tire circumferential direction, for example. However, the main groove 3 is not limited to such a form, and may extend in a wave shape or a zigzag shape, for example.

[0034] The distance L1 from the tire equator C to the groove centerline of the main groove 3 is, for example, 5% to 20% of the tread width TW. The tread width TW is the tire axial distance from one first ground contact edge T1 to the other first ground contact edge T1 in the normal state.

[0035] The groove width W1 of the main groove 3 is, for example, 4.0% to 7.0% of the tread width TW. The depth of the main groove 3 is, for example, 5 to 10 mm. However, the main groove 3 is not limited to this form.

[0036] The tread portion 2 includes a crown region 4 and two shoulder regions 5. The crown region 4 is divided between two main grooves 3. The shoulder region 5 is divided between one main groove 3 and the first ground contact end T1. The two shoulder regions 5 are provided in a manner of sandwiching the crown region 4. Thus, a main groove 3 and a shoulder region 5 are provided in the tread half region 2h between the tire equator C of the tread portion 2 and a first ground contact end T1.

[0037] Figure 2 An enlarged view of the shoulder area 5 is shown. Figure 2 As shown, at least one first inclined groove 6 inclined with respect to the tire axial direction is provided in the shoulder region 5. In the shoulder region 5 of the present embodiment, a plurality of first inclined grooves 6 are arranged in the tire circumferential direction.

[0038] The first inclined groove 6 extends in a manner that intersects at least the first ground contact end T1, the second ground contact end T2, and the third ground contact end T3. In addition, the depth of the first inclined groove 6 at the first ground contact end T1 is smaller than the depth of the first inclined groove 6 at the second ground contact end T2 and the third ground contact end T3. The tire 1 of the present invention can ensure wet performance and improve the steering stability during high-speed cornering (hereinafter, sometimes simply referred to as "steering stability") by adopting the above structure. As the reason for this, the following mechanism is inferred.

[0039] In the present invention, since the first inclined groove 6 extends in a manner intersecting each ground contact end, the first inclined groove 6 can exert a sufficient drainage effect and ensure wet performance even in a condition where the ground contact pressure is low (for example, the inner wheel during cornering, the rear wheel of an FF vehicle, etc.).

[0040] On the other hand, since the depth of the first inclined groove 6 at the first contact end T1 is smaller than the depth of the first inclined groove 6 at the second contact end T2 and the third contact end T3, it is considered that the rigidity near the first contact end T1 is improved, and the steering stability during high-speed cornering is improved.

[0041] The following describes a more detailed structure of the present embodiment. In addition, each structure described below shows a specific mode of the present embodiment. Therefore, it is self-evident that the present invention can exert the above-mentioned effect even if it does not have the structure described below. In addition, when any one of the structures described below is applied alone to the tire of the present invention having the above-mentioned characteristics, it is also possible to expect an improvement in the performance corresponding to each structure. Moreover, when several of the structures described below are applied in combination, it is possible to expect an improvement in the composite performance corresponding to each structure.

[0042] like Figure 1 As shown, the two shoulder regions 5 are substantially symmetrical with respect to the tire equator C, except that the phases of the grooves arranged therein are shifted in the tire circumferential direction. However, the present invention is not limited to such an embodiment.

[0043] In the present embodiment, the tire axial distance L2 from the tire equator C to the second ground contact end T2 is, for example, 35% to 45% of the tread width TW. In addition, the tire axial distance L3 from the tire equator C to the third ground contact end T3 is, for example, 25% to 35% of the tread width TW. In addition, such a structure can be obtained by appropriately adjusting the rubber thickness of the tread portion, the configuration of the tread reinforcement layer, and other well-known components.

[0044] In the shoulder region 5 of the present embodiment, in addition to the first inclined groove 6, a second inclined groove 7 and a third inclined groove 8 are provided. The detailed structure of the second inclined groove 7 and the third inclined groove 8 will be described later.

[0045] like Figure 2 As shown, a pitch length P1 of the first inclined groove 6 in the tire circumferential direction is, for example, greater than the tire axial width W2 of the shoulder region 5. Specifically, the pitch length P1 of the first inclined groove 6 is 1.20 to 2.00 times the width W2 of the shoulder region 5. Such first inclined grooves 6 can improve wet performance and steering stability in a balanced manner.

[0046] The length L4 of the first inclined groove 6 in the tire axial direction is, for example, 85% to 95% of the width W2 of the shoulder region 5. The first inclined groove 6 is inclined toward the opposite side of the rotation direction R of the tire 1 as it moves toward the tire axial outer side. Hereinafter, in this specification, such an inclined direction may be referred to as "inclined in the first direction relative to the tire axial direction".

[0047] The first inclined groove 6 is curved convexly, for example, toward the opposite side of the rotation direction R. The first inclined groove 6 has a curved vertex 6a, which is farthest from an imaginary straight line connecting the inner end 6i and the outer end 6o of the first inclined groove 6, on the groove edge farthest from the center of the curvature radius of the curve among the two groove edges. The first inclined groove 6 of the present embodiment is curved so as to have one curved vertex 6a.

[0048] The angle of the first inclined groove 6 relative to the tire axial direction is, for example, 10 to 45 degrees. In the present embodiment, the angle of the first inclined groove 6 at the third ground contact end T3 relative to the tire axial direction is greater than the angle of the first inclined groove 6 at the first ground contact end T1 relative to the tire axial direction. The above angle at the first ground contact end T1 is 25% to 35% of the above angle at the third ground contact end T3. Such a first inclined groove 6 improves the traction performance and the cornering performance on the wet road surface in a balanced manner. In addition, in this specification, the angle of the inclined groove is measured at the groove center line of the inclined groove.

[0049] Figure 3 FIG. 4 shows an enlarged view of the first inclined groove 6, the second inclined groove 7 and the third inclined groove 8. Figure 3 As shown, the first inclined groove 6 of the present embodiment has, for example, an axially inner end 6i of the tire that is interrupted in the shoulder region 5. The axial distance L5 from the third contact edge T3 to the axially inner end 6i of the first inclined groove 6 is, for example, the axial width W2 of the shoulder region 5 ( Figure 2 The first inclined groove 6 can exhibit high drainage performance even under a low ground pressure.

[0050] The outer end 6o of the first inclined groove 6 in the tire axial direction is located at a position axially outward from the first contact end T1. It is preferred that the distance L6 in the tire axial direction from the outer end 6o of the first inclined groove 6 to the first contact end T1 is smaller than the groove width W1 of the main groove 3 ( Figure 1 ), and is smaller than the distance L5. Specifically, the distance L6 is 5% to 10% of the width W2 of the shoulder region 5. Thus, the first inclined groove 6 can ensure wet performance and exhibit excellent steering stability.

[0051] A distance L7 in the tire axial direction from the second ground contact edge T2 to the curved apex 6a of the first inclined groove 6 is, for example, 15% or less of the width W2 of the shoulder region 5, and preferably 10% or less.

[0052] The first inclined groove 6 has a smaller groove width from the portion where the maximum groove width W3 is formed toward the inner end 6i and the outer end 6o. The maximum groove width W3 of the first inclined groove 6 is, for example, 80% to 120% of the groove width W1 of the main groove 3. Such a first inclined groove 6 contributes to a balanced improvement in wet performance and steering stability.

[0053] Figure 4 FIG. 1 is a diagram showing the cross-sectional shape of the first inclined groove 6. Figure 2 AA line section view. Figure 4As shown, the first inclined groove 6 includes an outer portion 11 intersecting the first grounding end T1 and a main body portion 12 intersecting the second grounding end T2 and the third grounding end T3.

[0054] The depth d1 of the outer portion 11 is, for example, 0.5 to 2.0 mm, preferably 0.8 to 1.2 mm. In addition, the length L8 of the outer portion 11 in the tire axial direction is equal to the length L4 of the first inclined groove 6 in the tire axial direction ( Figure 2 As shown, the same applies below. ) 15% to 25%. This can effectively improve the handling stability during high-speed cornering.

[0055] In this embodiment, the axial length of the area of ​​the outer portion 11 that is axially inward of the first contact end T1 is greater than the axial length of the area that is axially outward of the first contact end T1. As a result, the rigidity near the first contact end T1 is further improved, and the steering response during high-speed cornering becomes linear.

[0056] The main body portion 12 has a greater depth than the outer side portion 11. The maximum depth d2 of the main body portion 12 is, for example, 30% to 80% of the depth of the main groove 3. Thus, the rigidity of the shoulder region 5 is maintained and wet performance is ensured.

[0057] The main body 12 includes, for example, a central constant depth portion 12c, an outer inclined portion 12o, and an inner inclined portion 12i. The central constant depth portion 12c extends at a constant depth in the length direction of the first inclined groove 6. The outer inclined portion 12o decreases in depth from the central constant depth portion 12c toward the outer portion 11. The inner inclined portion 12i decreases in depth from the central constant depth portion 12c toward the inner end 6i of the first inclined groove 6. In the present embodiment, the central constant depth portion 12c intersects with the second grounding end T2 and the third grounding end T3. Thus, wetland performance is reliably ensured. In addition, Figure 3 In FIG. 1 , the boundaries of the outer portion 11 , the outer inclined portion 12 o , the central constant depth portion 12 c , and the inner inclined portion 12 i , and the chamfers provided at the groove edges are indicated by thin lines.

[0058] like Figure 2 As shown, in the shoulder region 5 of the present embodiment, a pair of the second inclined grooves 7 and the third inclined grooves 8 and the first inclined grooves 6 are alternately provided in the tire circumferential direction.

[0059] The second inclined groove 7 of the present embodiment does not overlap with the area formed by extending the first inclined groove 6 parallel to the tire axial direction, for example. The second inclined groove 7 intersects the second ground contact end T2 and the third ground contact end T3, and does not intersect the first ground contact end T1. In addition, the inner end 7i of the second inclined groove 7 in the tire axial direction is interrupted in the shoulder area 5. The length L9 of the second inclined groove 7 in the tire axial direction is, for example, 40% to 60% of the length L4 of the first inclined groove 6 in the tire axial direction. Such a second inclined groove 7 can cooperate with the first inclined groove 6 to exert excellent wet performance.

[0060] The second inclined groove 7 is inclined in the first direction with respect to the tire axial direction. The angle of the second inclined groove 7 with respect to the tire axial direction is, for example, 15 to 45 degrees.

[0061] The second inclined groove 7 is curved convexly, for example, toward the opposite side of the rotation direction R. The second inclined groove 7 has a curved vertex 7a which is farthest from a straight line connecting the inner end 7i and the outer end 7o of the second inclined groove 7, on the groove edge farthest from the center of the curvature radius of the curve among the two groove edges. The second inclined groove 7 of the present embodiment is curved so as to have one curved vertex 7a.

[0062] like Figure 3 As shown, the distance L10 in the tire axial direction from the third ground contact end T3 to the inner end 7i of the second inclined groove 7 in the tire axial direction is smaller than the distance L5 in the tire axial direction from the third ground contact end T3 to the inner end 6i of the first inclined groove 6. Specifically, the distance L10 from the third ground contact end T3 to the inner end 7i of the second inclined groove 7 in the tire axial direction is 5% to 20% of the width W2 of the shoulder region 5. Such a second inclined groove 7 can exhibit excellent drainage even when the ground contact pressure is small.

[0063] The outer end 7o of the second inclined groove 7 on the outer side in the tire axial direction is located between the first ground contact end T1 and the second ground contact end T2. It is preferred that the distance L11 from the outer end 7o of the second inclined groove 7 to the first ground contact end T1 in the tire axial direction is smaller than the groove width W1 of the main groove 3. Specifically, the distance L11 is 5% to 15% of the width W2 of the shoulder region 5. Thus, the wet performance can be more reliably ensured.

[0064] A distance L12 in the tire axial direction from the second ground contact edge T2 to the bending apex 7a of the second inclined groove 7 is, for example, 10% or less of the width W2 of the shoulder region 5, and preferably 5% or less.

[0065] The second inclined groove 7 has a groove width that decreases from the portion where the maximum groove width W4 is formed toward the inner end 7i and the outer end 7o. The maximum groove width W4 of the second inclined groove 7 is, for example, the groove width W1 ( Figure 1Such second inclined grooves 7 can maintain the rigidity of the shoulder region 5 and exhibit excellent drainage performance.

[0066] Figure 5 FIG. 2 is a diagram showing the cross-sectional shape of the second inclined groove 7. Figure 2 BB line cross-sectional view. Figure 5 As shown, the second inclined groove 7 includes: a first portion 16 intersecting the third grounding end T3; and a second portion 17 intersecting the second grounding end T2.

[0067] The first portion 16 has a depth that decreases as it moves toward the inner side of the tire axial direction, for example. In addition, the second portion 17 has a constant depth in the longitudinal direction of the second inclined groove 7. The depth d3 of the second portion 17 is, for example, 30% to 80% of the depth of the main groove 3. Such a second portion 17 improves wet performance and steering stability in a balanced manner.

[0068] The second inclined groove 7 includes a third portion 18 having a smaller depth than the second portion 17 on the outer side of the second portion 17 in the tire axial direction. In the present embodiment, an inclined portion 17o is formed whose depth decreases as it moves from the second portion 17 toward the third portion 18. The depth d4 of the third portion 18 is, for example, 0.5 to 2.0 mm, preferably 0.8 to 1.2 mm. The length L13 of the third portion 18 in the tire axial direction is, for example, the length L9 ( Figure 2 Such a third portion 18 improves the wet performance and the steering stability in a balanced manner.

[0069] like Figure 2 As shown, in order to further enhance the above effect, the third inclined groove 8 is provided, for example, between the third ground contact end T3 and the main groove 3. Both ends of the third inclined groove 8 are interrupted inside the shoulder region 5. The length L14 of the third inclined groove 8 in the tire axial direction is, for example, 15% to 25% of the width W2 of the shoulder region 5.

[0070] It is preferable that the third inclined groove 8 does not overlap with a region formed by extending the second inclined groove 7 in parallel with the tire axial direction. Such a third inclined groove 8 can exert the above-mentioned effect and suppress uneven wear of the shoulder region 5.

[0071] The third inclined groove 8 is inclined in the first direction relative to the tire axial direction. The angle of the third inclined groove 8 relative to the tire axial direction is, for example, 50 to 70 degrees. In this embodiment, the third inclined groove 8 is inclined at a larger angle than the first inclined groove 6 and the second inclined groove 7 relative to the tire axial direction.

[0072] like Figure 3As shown, the distance L15 in the tire axial direction from the third ground contact end T3 to the inner end 8i of the third inclined groove 8 in the tire axial direction is greater than the distance L5 in the tire axial direction from the third ground contact end T3 to the inner end 6i of the first inclined groove 6. Specifically, the distance L15 in the tire axial direction from the third ground contact end T3 to the inner end 8i of the third inclined groove 8 is, for example, 30% to 40% of the width W2 in the tire axial direction of the shoulder region 5. Thus, when running on wet ground, water discharged from the third inclined groove 8 is guided to the second inclined groove 7 side, and higher drainage performance is exhibited.

[0073] The outer end 8o of the third inclined groove 8 on the outer side in the tire axial direction is located on the outer side in the tire axial direction than the inner end 6i of the first inclined groove 6 and on the inner side in the tire axial direction than the inner end 7i of the second inclined groove 7. The distance L16 in the tire axial direction from the third ground contact end T3 to the outer end 8o of the third inclined groove 8 is, for example, 10% to 20% of the width W2 of the shoulder region 5. Such a third inclined groove 8 can complement the drainage performance of the first inclined groove 6 and the second inclined groove 7.

[0074] The third inclined groove 8 has a smaller groove width from the center portion in the longitudinal direction toward the inner end 8i and the outer end 8o. The maximum groove width W5 of the third inclined groove 8 is smaller than the groove width W1 of the main groove 3, the groove width W3 of the first inclined groove 6, and the groove width W4 of the second inclined groove 7. Specifically, the groove width W5 of the third inclined groove 8 is 30% to 50% of the groove width W1 of the main groove 3. Such a third inclined groove 8 can improve drainage without impairing steering stability.

[0075] In order to effectively prevent the reduction of steering stability, the maximum depth of the third inclined groove 8 is, for example, smaller than the maximum depth of the first inclined groove 6, and smaller than the maximum depth of the second inclined groove 7. The depth of the third inclined groove 8 of the present embodiment is, for example, 0.5 to 2.0 mm, preferably 0.8 to 1.2 mm. In addition, the third inclined groove 8 has a constant depth in its longitudinal direction.

[0076] Figure 6 An enlarged view of the crown region 4 is shown. Figure 6 As shown, the width W6 of the crown region 4 in the tire axial direction is, for example, 15% to 25% of the tread width TW.

[0077] It is preferred that the crown region 4 is provided with, for example, the first sipe 21 and the second sipe 22. In the present specification, a "sipe" refers to a groove element having a small width, and the width between two groove walls facing each other is 1.5 mm or less. The above-mentioned width of the sipe is preferably 0.3 to 1.2 mm, and more preferably 0.5 to 1.0 mm. In the present specification, in the cross section of a certain groove element, for an element in which an area with a width of less than 1.5 mm accounts for more than 50% of its total width, even if a part of it includes an area with a width of more than 1.5 mm, it is treated as a sipe (including a sipe of a groove element). In addition, in the cross section of a certain groove element, for an element in which an area with a width greater than 1.5 mm accounts for more than 50% of its total width, even if a part of it includes an area with a width of less than 0.6 mm, it is treated as a groove (including a groove of a sipe element).

[0078] The first sipe 21 extends from one main groove 3 and is interrupted in the crown region 4. The second sipe 22 extends from the other main groove 3 and is interrupted in the crown region 4. The axial length L17 of the first sipe 21 and the axial length L18 of the second sipe 22 are, for example, 25% to 35% of the axial width W6 of the crown region 4. Thus, the crown region 4 has a continuous portion in the tire circumferential direction. The first sipe 26 and the second sipe 27 improve the wet performance and the steering stability in a balanced manner.

[0079] The first sipes 21 and the second sipes 22 are inclined toward the tire equator C from the connected main groove 3, and are opposite to the tire rotation direction R. The angle of the first sipes 21 and the second sipes 22 relative to the tire axial direction is, for example, 10° or less. Thus, the traction performance on wet roads is improved.

[0080] As mentioned above, although the tire which concerns on one embodiment of this invention was demonstrated in detail, this invention is not limited to the said specific embodiment, It can be implemented by changing into various forms.

[0081] Example

[0082] Based on the specifications in Table 1, we have produced Figure 1 A pneumatic tire with a basic pattern of 205 / 55R16 was produced as a comparative example. Figure 1 The tires tested had a basic pattern of and the depth of the first inclined groove at the first contact end was the same as the depth of the second contact end and the third contact end of the first inclined groove. The test tires had substantially the same structure except for the above points. The high-speed cornering handling stability and wet performance of the test tires were tested. The common specifications and test methods of the test tires are as follows.

[0083] Installed rim: 16×6.5J

[0084] Tire internal pressure: 230kPa

[0085] Test vehicle: 2000cc displacement, FR vehicle

[0086] Tire mounting position: All wheels

[0087] <Handling stability during high-speed cornering>

[0088] The handling stability of the test vehicle when turning at high speed on a circular track consisting of dry road surface was evaluated by the driver's sense. The results were expressed as a score with the comparative example being rated as 100, and the larger the value, the better the handling stability when turning at high speed.

[0089] <Wetland Performance>

[0090] The wet performance of the test vehicle when driving on a normal road consisting of a wet road surface was evaluated by the driver's senses. The results were expressed as a score with the comparative example being rated as 100, and the larger the value, the better the wet performance.

[0091] The test results are shown in Table 1.

[0092] Table 1:

[0093]

[0094] The test results confirmed that the tire of the example ensures wet performance and improves handling stability during high-speed cornering.

Claims

1. A pneumatic tire having a tread portion, characterized in that: The invention comprises: a first grounding end, a second grounding end and a third grounding end when the wheel rim is assembled with respect to the regular wheel rim at the regular internal pressure and 100%, 75% and 50% of the regular load are applied and the wheel rim is grounded with the flat surface at the camber angle of 0°, The second ground contact end is located on the inner side of the tire axial direction than the first ground contact end. The third ground contact end is located inward of the second ground contact end in the tire axial direction and on both sides of the tire equator. The distance in the tire axial direction from the third ground contact edge to the tire equator of the tread portion is 25% to 35% of the tread width. A main groove extending continuously in the tire circumferential direction between the third ground contact end and the tire equator and a shoulder area divided between the main groove and the first ground contact end are provided in a tread half region between the tire equator and one of the first ground contact ends of the tread portion. At least one first inclined groove is provided in the shoulder region and is inclined relative to the tire axial direction. The first inclined groove extends in a manner intersecting at least the first grounding end, the second grounding end, and the third grounding end. The depth of the first inclined groove at the first ground contact end is smaller than the depth of the first inclined groove at the second ground contact end and the third ground contact end.

2. The pneumatic tire according to claim 1, characterized in that The tread portion includes: the two main grooves disposed so as to sandwich the tire equator; a crown region defined between the two main grooves; and the two shoulder regions disposed so as to sandwich the crown region.

3. The pneumatic tire according to claim 1 or 2, characterized in that: The tire rotation direction is specified, The first inclined groove is inclined toward the side opposite to the tire rotation direction as it goes toward the outer side in the tire axial direction.

4. The tire according to claim 1 or 2, characterized in that: The first inclined groove includes an outer portion intersecting the first grounding end and a main portion intersecting the second grounding end and the third grounding end and having a greater depth than the outer portion.

5. The tire according to claim 1 or 2, characterized in that: An angle of the first inclined groove at the third ground contact end relative to the tire axial direction is greater than an angle of the first inclined groove at the first ground contact end relative to the tire axial direction.

6. The pneumatic tire according to claim 1 or 2, characterized in that: In the shoulder region, at least one second inclined groove is provided which is inclined relative to the tire axial direction. The second inclined groove intersects the second grounding end and the third grounding end, and does not intersect the first grounding end.

7. The pneumatic tire according to claim 6, characterized in that: The second inclined groove includes a first portion intersecting with the third grounding end, The depth of the first portion decreases toward the inner side in the tire axial direction.

8. The pneumatic tire according to claim 6, wherein: The second inclined groove includes a second portion intersecting with the second grounding end, The second portion has a constant depth in the longitudinal direction of the second inclined groove.

9. The pneumatic tire according to claim 6, wherein: The length of the second inclined groove in the tire axial direction is 40% to 60% of the length of the first inclined groove in the tire axial direction.

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