pneumatic tires

Abstract

Pneumatic tires with a mounting direction indicator section that shows a mounting direction of a tire in relation to a vehicle; and a tread surface in which an outside and an inside are asymmetrical in a vehicle width direction in relation to an equatorial plane of the tire; wherein the tread surface comprises a first main groove extending in a tire circumferential direction at a position outside the equatorial plane of the tire in the vehicle width direction, a second main groove extending in the tire circumferential direction at a position closer to the equatorial plane of the tire than the first main groove, a third main groove extending in the tire circumferential direction at a position inwards to the equatorial plane of the tire in the vehicle width direction, and a fourth main groove extending in the tire circumferential direction at a position farther from the equatorial plane of the tire than the third main groove; where the relationships 1.05 ≤ G1 / G3 ≤ 1.25, 1.20 ≤ G2 / G3 ≤ 1.40 and 1.10 ≤ G4 / G3 ≤ 1.30 are satisfied; and the relationships G3 < G1 < G2 and G3 < G1 < G4 are satisfied where G1 is a groove width of the first main groove, G2 is a groove width of the second main groove, G3 is a groove width of the third main groove, and G4 is a groove width of the fourth main groove.

Description

Technical field

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

[0002] There is a need for known pneumatic tires to provide compatible steering stability on dry and wet roads and noise performance with respect to pass-by noise. Technologies known as pneumatic tires in connection with such a requirement are those described in WO 2015 / 005194 A1 and JP 5695476 B2. The prior art also includes documents US 2013 / 0 112 325 A1, US 2014 / 0 305 559 A1, and EP 1 792 754 A1. Brief description of the invention: Technical problem

[0003] The pneumatic tires described in WO 2015 / 005194 A1 and JP 5695476 B2 offer room for improvement in terms of providing compatible steering stability on dry and wet road surfaces and noise performance with respect to pass-by noise.

[0004] One object of the present invention is to provide a pneumatic tire that can provide steering stability performance on dry and wet road surfaces and noise performance in a highly compatible manner. Solution to the problem

[0005] To solve the problem described above, one aspect of the present invention provides a pneumatic tire comprising a mounting direction indicator section that indicates a mounting direction of a tire in relation to a vehicle; and a tread surface in which an outside and an inside are asymmetrical in a vehicle width direction with respect to an equatorial plane of the tire;wherein the tread surface has a first main groove extending in a tire circumferential direction at a position outside the equatorial plane of the tire in the vehicle width direction, a second main groove extending in the tire circumferential direction at a position closer to the equatorial plane of the tire than the first main groove, a third main groove extending in the tire circumferential direction at a position inwards to the equatorial plane of the tire in the vehicle width direction, and a fourth main groove extending in the tire circumferential direction at a position farther from the equatorial plane of the tire than the third main groove; wherein the relationships 1.05 ≤ G1 / G3 ≤ 1.25, 1.20 ≤ G2 / G3 ≤ 1.40 and 1.10 ≤ G4 / G3 ≤ 1.30 are satisfied;and the relationships G3 < G1 < G2 and G3 < G1 < G4 are satisfied, where G1 is a groove width of the first main groove, G2 is a groove width of the second main groove, G3 is a groove width of the third main groove, and G4 is a groove width of the fourth main groove.;

[0006] Furthermore, the groove width G2 of the second main groove and the groove width G4 of the fourth main groove preferably exhibit a relationship G4 < G2.

[0007] The groove width G1 of the first main groove, the groove width G2 of the second main groove and the groove width G3 of the third main groove preferably have a relationship (G2 - G1) / G3 ≥ 0.01.

[0008] For the width of an outer web section between the first main groove and the second main groove, the width of a middle web section between the second main groove and the third main groove, and the width of an inner web section between the third main groove and the fourth main groove, the ratio of a maximum width to a minimum width is preferably less than or equal to 1.05.

[0009] For a width of an outer rib section between the first main groove and the second main groove, a width of a middle rib section between the second main groove and the third main groove, and a width of an inner rib section between the third main groove and the fourth main groove, at least one of the widths may differ from the other widths.

[0010] Preferably, the pneumatic tire further comprises a first narrow groove which extends in the circumferential direction of the tire at a position further inwards than the fourth main groove in the vehicle width direction, and a groove width Gs of the first narrow groove and the groove width G3 of the third main groove has a relationship of 0.10 ≤ Gs / G3 ≤ 0.30.

[0011] Preferably, the pneumatic tire further comprises a second narrow groove provided in the inner rib section and extending in the circumferential direction of the tire, and a groove width Gr of the second narrow groove and the groove width G3 of the third main groove have a relationship of 0.10 ≤ Gr / G3 ≤ 0.30.

[0012] In the inner web section, the second narrow groove is preferably provided at a position where the ratio of a distance from the third main groove to a length of the inner web section in the vehicle width direction is greater than or equal to 0.15 and less than or equal to 0.30.

[0013] The pneumatic tire preferably further comprises a first tread groove which opens at a first end to the second narrow groove and at a second end to the fourth main groove.

[0014] Preferably, the first cleat groove has a groove width that varies between the first end and the second end, and a relationship between a groove width W1 at the first end and a groove width W2 at the second end is in the range of 0.20 ≤ W1 / W2 ≤ 0.60.

[0015] The pneumatic tire preferably further comprises a second lug groove which opens at a first end towards the first main groove and extends outwards in the direction of the vehicle width at a second end; and a slat which is connected at a first end to the second end of the second lug groove and extends outwards in the direction of the vehicle width at a second end.

[0016] Preferably, the pneumatic tire further comprises a third lug groove that extends further outwards in the vehicle width direction from a position further than the first main groove in the vehicle width direction; and a fourth lug groove that extends further inwards in the vehicle width direction from a position further than the fourth main groove in the vehicle width direction, wherein the third lug groove does not open towards the first main groove and the fourth lug groove does not open towards the fourth main groove.

[0017] The distance from the equatorial plane of the tire to the second main groove is preferably shorter than the distance from the equatorial plane of the tire to the third main groove. Advantageous effects of the invention

[0018] An air-filled tire according to an embodiment of the present invention can provide steering stability on dry and wet road surfaces and noise performance in a highly compatible manner. Brief description of the drawings Fig. Figure 1 is a meridian cross-sectional view illustrating a pneumatic tire according to an embodiment of the present invention. Fig. Figure 2 is a flattened view illustrating a tread pattern of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 3 is a partially enlarged view of the tread pattern of Fig. 2. Description of embodiments

[0019] Pneumatic tires according to embodiments of the present invention are described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, components of the embodiments include elements that are interchangeable while maintaining conformity with the invention, as well as obviously interchangeable elements. In addition, the modified examples described in the embodiments can be combined as required within the scope of protection obvious to a person skilled in the art. pneumatic tires

[0020] Fig. Figure 1 is a cross-sectional view in a tire meridian direction illustrating a pneumatic tire according to an embodiment of the invention. Fig. Figure 1 illustrates a cross-sectional view of a half-area in the tire radial direction. Fig.Figure 1 also illustrates a radial tire for a passenger car as an example of a pneumatic tire.

[0021] Herein, "tire radial direction" refers to the direction perpendicular to the axis of rotation (not illustrated) of a pneumatic tire 10. "Inward in tire radial direction" refers to the direction toward the axis of rotation in the tire radial direction. "Outward in tire radial direction" refers to the direction away from the axis of rotation in the tire radial direction. "Circular direction" also refers to the circumferential direction, with the central axis being the axis of rotation. Furthermore, "lateral direction" refers to the direction parallel to the axis of rotation. "Inward in tire lateral direction" refers to the direction toward the equatorial plane of the tire CL in the lateral direction, and "outward in tire lateral direction" refers to the direction away from the equatorial plane of the tire CL in the lateral direction.“Tire equatorial plane CL” refers to a plane perpendicular to the axis of rotation of the pneumatic tire 10 and passing through the center of the tire width of the pneumatic tire 10. “Tire width” is the width in the transverse direction of the tire between components located on the outer side of the tire, or in other words, the distance between the components furthest from the tire equatorial plane CL in the transverse direction. “Tire equator line” refers to a line lying on the tire equatorial plane CL and extending along the circumferential direction of the pneumatic tire 10. In the present embodiment, the tire equator line and the tire equatorial plane are designated by the same reference numeral CL.

[0022] Referring to the same drawing, "cross-section in a tire meridian direction" refers to a cross-section of the tire along a plane that includes the tire's axis of rotation (not shown). The reference symbol CL denotes the equatorial plane of the tire and refers to a plane perpendicular to the tire's axis of rotation and passing through the tire's center point in the direction of the tire's axis of rotation. "Tire transverse direction" refers to the direction parallel to the tire's axis of rotation. "Tire radial direction" refers to the direction perpendicular to the tire's axis of rotation.

[0023] Furthermore, the inside and outside sides in the direction of vehicle width are defined when the tire is mounted on the vehicle. Specifically, the pneumatic tire 10 includes a mounting direction indicator (not illustrated) that shows the mounting direction relative to a vehicle. The mounting direction indicator consists, for example, of a marking or ridges / grooves on a sidewall section of the tire. For example, Regulation 30 of the Economic Commission for Europe (ECE R30) requires that a mounting direction indicator be provided on the sidewall section corresponding to the outside sidewall in the direction of vehicle width when the tire is mounted on the vehicle.

[0024] As in Fig.As illustrated in Figure 1, the pneumatic tire 10 of the present embodiment comprises an annular tread section 1 extending in the circumferential direction of the tire, a pair of sidewall sections 2, 2 which are arranged on both sides of the tread section 1, and a pair of bead sections 3, 3 which are arranged inwards from the sidewall sections 2 in the radial direction of the tire.

[0025] A carcass layer 4 is mounted between the pair of bead sections 3, 3. The carcass layer 4 includes a plurality of reinforcing cord threads extending in the tire radial direction and is folded back from one tire inner to one tire outer surface around tire bead cores 5, which are arranged in each of the tire bead sections 3. A bead filler 6 with a triangular cross-sectional shape, formed from a rubber compound, is arranged on the outer circumference of the bead core 5.

[0026] A plurality of belt layers 7 are embedded on an outer circumferential side of the carcass layer 4 in the tread section 1. Each belt layer 7 contains a plurality of reinforcing cord threads inclined with respect to the tire's circumferential direction, the reinforcing cord threads of the different layers being arranged crosswise. In the belt layers 7, the angle of inclination of the reinforcing cord threads with respect to the tire's circumferential direction is set to a range of, for example, 10° to 40°. Steel cord threads are preferably used as the reinforcing cord threads of the belt layers 7. To improve high-speed resistance, at least one belt cover layer 8, formed by arranging reinforcing cord threads at an angle of, for example, less than or equal to 5° with respect to the tire's circumferential direction, is arranged on an outer circumferential side of the belt layers 7.Preferably, nylon, aramid or similar organic fiber cord threads are used as the reinforcing cord threads of the belt cover layer 8.

[0027] It should be noted that the tire internal structure described above is a typical example of a pneumatic tire and that pneumatic tires are not limited to this. tread section

[0028] Fig. 2 is a unfolded view showing a tread pattern of the in Fig. 1 illustrated pneumatic tire 10 illustrated. Fig. Figure 3 is a partially enlarged view of the tread pattern of Fig. 2. In Fig. 2 denotes the reference symbol T as a ground contact edge.

[0029] As in Fig.As illustrated in Figure 2, the pneumatic tire 10 comprises the tread section 1, which includes a first main groove 11 extending circumferentially at a position outside the equatorial plane of the tire CL in the vehicle width direction, a second main groove 12 extending circumferentially at a position closer to the equatorial plane of the tire CL than the first main groove 11, a third main groove 13 extending circumferentially at a position inwards from the equatorial plane of the tire CL in the vehicle width direction, and a fourth main groove 14 extending circumferentially at a position farther from the equatorial plane of the tire CL than the third main groove 13.

[0030] The groove width of the first main groove 11 is designated G1, the groove width of the second main groove 12 is designated G2, the groove width of the third main groove 13 is designated G3, and the groove width of the fourth main groove 14 is designated G4. The groove widths then have the following relationships: 1.05≤G1 / G3≤1.25, 1.20≤G2 / G3≤1.40 and 1.10≤G4 / G3≤1.30.

[0031] Additionally, the groove width G1 of the first main groove 11, the groove width G2 of the second main groove 12, and the groove width G3 of the third main groove 13 have the relationships G3 < G1 < G2 and G3 < G1 < G4, respectively. Furthermore, the groove width G2 of the second main groove 12 and the groove width G4 of the fourth main groove 14 preferably have the relationship G4 < G2. In other words, the groove width G1 of the first main groove 11, the groove width G2 of the second main groove 12, the groove width G3 of the third main groove 13, and the groove width G4 of the fourth main groove 14 preferably differ from one another. By making the circumferential width of each main groove different from the circumferential width of all other main grooves in order to vary the resonance of the air flowing through the tire grooves, the air column resonance can be disrupted to improve noise performance. The relationship G3 < G1 < G4 < G2 is preferable for improving noise performance.

[0032] The groove width G1 of the first main groove 11, the groove width G2 of the second main groove 12, and the groove width G3 of the third main groove 13 preferably have the ratio (G2 - G1) / G3 ≥ 0.01. In other words, the ratio (G2 - G1) / G3 of the difference between the groove width G1 and the groove width G2 to the groove width G3 is preferably greater than or equal to 0.01. The groove width on the outer side in the tire's transverse direction is narrower than the groove width on the central side near the equatorial plane of the tire CL. This is effective in reducing the vehicle's pass-by noise without compromising wet steering stability.

[0033] It should be noted that, as in Fig.Figure 2 illustrates that in the case of a pneumatic tire 10, the distance D12 from the equatorial plane of the tire CL to the second main groove 12 is shorter than the distance D13 from the equatorial plane of the tire CL to the third main groove 13. That is, the ratio of distance D12 to distance D13 is D12 / D13 < 1.0. Thus, the pneumatic tire 10 has a tread surface in which an outer and an inner side are asymmetrical in a vehicle width direction with respect to an equatorial plane of the tire CL.

[0034] The first main groove 11, the second main groove 12, the third main groove 13, and the fourth groove 14 are each a "circumferential groove" with a wear indicator that shows the final state of wear and typically have a groove width of more than or equal to 5.0 mm and a groove depth of more than or equal to 7.5 mm. It should be noted that the groove width and groove depth of the first main groove 11, the second main groove 12, the third main groove 13, and the fourth main groove 14 are not limited to the ranges described above.

[0035] Additionally, "groove" as described below refers to a lateral groove with a groove width of more than or equal to 2.0 mm and a groove depth of more than or equal to 3.0 mm. Additionally, "lamella" as described below refers to a notch formed in a web section, typically having a groove width of less than 1.5 mm. Bridge section, tunnel groove and narrow groove

[0036] The tread section 1, which is provided with the first main groove 11, the second main groove 12, the third main groove 13 and the fourth main groove 14, is thus subdivided into a plurality of rib sections. In particular, the tread section 1 comprises an outer shoulder rib section So, which is positioned further outwards than the first main groove 11 in the vehicle width direction, an outer rib section Ro between the first main groove 11 and the second main groove 12, a central rib section Rc between the second main groove 12 and the third main groove 13, an inner rib section Ri between the third main groove 13 and the fourth main groove 14 and an inner shoulder rib section Si, which is positioned further inwards than the fourth main groove 14 in the vehicle width direction.

[0037] The outer shoulder rib section So of the tread section 1 comprises second lug grooves 31, each opening at a first end towards the first main groove 11 and extending outwards in the vehicle width direction at a second end; sipes 40, each connected at a first end to the second end of the second lug groove 31 and extending outwards in the vehicle width direction at a second end; and third lug grooves 32, extending outwards in the vehicle width direction from a position further outwards than the first main groove 11. The second lug grooves 31 and the sipes 40 are provided at regular intervals in the circumferential direction of the tire. The provision of the sipes 40 effectively ensures steering stability performance on wet road surfaces without reducing the stiffness of the outer shoulder rib section So.The third lug grooves 32 are arranged at regular intervals in the direction of the tire's circumference. It is important to note that the third lug grooves 32 do not open towards the first main grooves 11. Improved noise performance can be achieved by preventing the third lug grooves 32 of the outer shoulder rib section So from contacting the first main groove 11.

[0038] In the tread section 1, the outer rib section Ro comprises sixth lug grooves 35, each opening at a first end towards the second main groove 12, and seventh lug grooves 36, each opening at a first end towards the first main groove 11. The sixth lug grooves 35 are arranged at regular intervals in the tire's circumferential direction. The seventh lug grooves 36 are also arranged at regular intervals in the tire's circumferential direction. Each of the sixth lug grooves 35 terminates at a second end in the outer rib section Ro. Each of the seventh lug grooves 36 terminates at a second end in the outer rib section Ro. In the outer rib section Ro, the sixth lug grooves 35 and the seventh lug grooves 36 are arranged alternately in the tire's circumferential direction.

[0039] It should be noted that the sixth tunnel groove 35 may or may not have a recessed section at its first end that opens to the second main groove 12. The seventh tunnel groove 36 may or may not have a recessed section at its first end that opens to the first main groove 11.

[0040] The central rib section Rc of the tread section 1 comprises fifth lug grooves 34, each opening at a first end towards the third main groove 13. The fifth lug groove 34 may or may not have a recessed section at its first end that opens towards the first main groove 13. The fifth lug grooves 34 are arranged at regular intervals in the circumferential direction of the tire. The fifth lug groove 34 terminates at a second end within the central rib section Rc. The second end of the fifth lug groove 34 does not cross the equatorial plane CL.

[0041] The inner rib section Ri of the tread section 1 comprises a second narrow groove 16 extending in the circumferential direction of the tire; and first lug grooves 30, each opening at one end to the second narrow groove 16 and at the other end to the fourth main groove 14. By arranging the second narrow groove 16, which extends in the circumferential direction of the tire, on the inner side in the direction of the vehicle width, the stiffness of the laterally outer rib section can be ensured, and steering stability and improved drainage characteristics can be achieved in a compatible manner. The first lug grooves 30 are connected to the second narrow groove 16 and the fourth main groove 14. The first lug grooves 30 are provided at regular intervals in the circumferential direction of the tire.The groove width Gr of the second narrow groove 16 and the groove width G3 of the third main groove 13 preferably have the relationship 0.10 ≤ Gr / G3 ≤ 0.30. Steering stability can be ensured by arranging the first lug grooves 30, extending in the transverse direction of the tire, on the inside of the inner rib section Ri in the vehicle width direction. Furthermore, the drainage properties can be ensured by a connection between the second narrow groove 16 and the fourth main groove 14 via the first lug grooves 30.

[0042] The inner shoulder rib section Si of the tread section 1 comprises a first narrow groove 15 extending circumferentially at a position further inward than the fourth main groove 14 in the vehicle width direction; and fourth lug grooves 33 extending in the vehicle width direction from a position further inward than the fourth main groove 14. The groove width Gs of the first narrow groove 15 and the groove width G3 of the third main groove 13 preferably have the relationship 0.10 ≤ Gs / G3 ≤ 0.30. It should be noted that the fourth lug grooves 33 do not open toward the fourth main groove 14. Improved noise performance can be achieved by preventing the fourth lug grooves 33 in the inner shoulder rib section Si from communicating with the fourth main groove 14.

[0043] Additionally, for the width of the outer rib section Ro, the width of the central rib section Rc, and the width of the inner rib section Ri, the ratio of the maximum width to the minimum width is preferably less than or equal to 1.05. A ratio of less than or equal to 1.05 means that the width of the outer rib section Ro, the width of the central rib section Rc, and the width of the inner rib section Ri are essentially equal. The essentially equal width of the rib sections results in uniform stiffness of the rib sections. Thus, the resistance performance under uneven wear is improved, and the uniformity of the pneumatic tire 10 can be enhanced.

[0044] For the width of the outer rib section Ro between the first main groove 11 and the second main groove 12, the width of the middle rib section Rc between the second main groove 12 and the third main groove 13, and the width of the inner rib section Ri between the third main groove 13 and the fourth main groove 14, each of the widths can differ from all the other widths, or each of the widths can be the same as each of the other widths. At least one of the widths of the outer rib section Ro, the width of the middle rib section Rc, and the width of the inner rib section Ri can differ from the other widths. By varying the widths of the rib sections, adjusting their widths allows the handling performance to be adjusted in a case where the camber angle in the vehicle is set to an angle other than 0 degrees.

[0045] In Fig.In section 3, the length of the inner web section in the vehicle width direction is designated D1, and the distance from an inner end section of the third main groove 13 in the vehicle width direction to a center line 161 of the second narrow groove 16 is designated D2. The ratio of the distance D2 to the length D1 is preferably greater than or equal to 0.15 and less than or equal to 0.30. In other words, the second narrow groove 16 is preferably provided at a position where the ratio of the distance D2 from the third main groove 13 to the length D1 of the inner web section Ri in the vehicle width direction is preferably greater than or equal to 0.15 and less than or equal to 0.30. By arranging the second narrow groove 16 in this area, adequate stiffness of the inner web section Ri can be ensured.

[0046] The first groove 30 comprises a first groove section 30A and a second groove section 30B. The groove width W1 of the first groove section 30A is smaller than the groove width W2 of the second groove section 30B. The groove width W1 has the maximum value of the groove width of the first groove section 30A. The groove width W2 has the maximum value of the groove width of the second groove section 30B. It should be noted that, excluding a recess section 140, the groove width W2 is measured with reference to an imaginary line 141 obtained by extending a groove wall.

[0047] As in Fig.As illustrated in Figure 3, the groove width of the first lug groove 30 varies between the first end, which opens into the second narrow groove 16, and the second end, which opens into the fourth main groove 14. For the first lug groove 30, the relationship between the groove width W1 at the first end and the groove width W2 at the second end is preferably in the range of 0.20 ≤ W1 / W2 ≤ 0.60. In other words, in the first lug groove 30, the groove width of the section near the inside in the vehicle width direction is greater than the groove width of the section near the equatorial plane of the tire CL. By increasing the groove width of the first lug groove 30 on the inside in the vehicle width direction, the drainage characteristics can be effectively improved.

[0048] The groove width is the maximum distance between the left and right groove walls at the groove opening section and is measured when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state. In configurations where the groove sections include recessed sections or chamfered sections on their edges, the groove width is measured with reference to the points of intersection where, viewed in a cross-sectional view perpendicular to the groove's longitudinal direction, the tread contact surface and extension lines of the groove walls meet. Additionally, in configurations where the grooves extend in a zigzag or wave-like manner around the tire's circumference, the groove width is measured with reference to the centerline of the groove wall amplitude.

[0049] The ground contact edge of the tire T is defined as the position of maximum width in the tire axial direction of the contact surface between the tire and a flat plate when the tire is mounted on a predetermined rim, inflated to the predetermined internal pressure, placed vertically on the flat plate in a static state, and loaded with a load corresponding to the predetermined load.

[0050] "Specified rim" refers to an "applicable rim" as defined by the Japan Automobile Tyre Manufacturers Association Inc. (JATMA), a "design rim" as defined by the Tire and Rim Association, Inc. (TRA), or a "measuring rim" as defined by the European Tyre and Rim Technical Organisation (ETRTO). "Specified inflation pressure" refers to a "maximum air pressure" as defined by JATMA, the maximum value in "tire load limits at various cold inflation pressures" as defined by the TRA, and "inflation pressures" as defined by the ETRTO.Furthermore, "specified load" refers to a "maximum load capacity" as defined by JATMA, the maximum value in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or "LOAD CAPACITY" as defined by ETRTO. However, in the case of JATMA, the specified internal pressure for a passenger car tire is 180 kPa, and the specified load is 88% of the maximum load capacity. Examples

[0051] Tables 1 to 3 show the performance test results of pneumatic tires according to embodiments of the present invention. In the performance tests, various pneumatic tires were evaluated with regard to their dry steering stability performance, their wet steering stability performance, and their noise performance. For these performance tests, test tires with a size of 225 / 60R18 100H were mounted on rims with a rim size of 17×7.5 JJ and inflated to an air pressure of 240 kPa. Additionally, a sport utility vehicle (SUV) with a front-engine, front-wheel drive (FF) and an engine displacement of 2400 cm³ was used as the test vehicle. 3 used.

[0052] To assess dry steering stability performance, the test vehicle was driven on a dry road surface with shallow circular sections at speeds ranging from 60 km / h to 100 km / h. The test driver then performed a sensory evaluation of steering during lane changes and cornering, as well as stability while driving forward. The results of this evaluation are expressed as index values ​​and assessed using the state of the art as a reference value (100). Higher values ​​are preferred in this evaluation.

[0053] To assess wet steering stability, the test vehicle was driven at 40 km / h on an asphalt surface covered with 1 mm of water. The test driver then performed a sensory evaluation of steering during lane changes and cornering, as well as stability while driving forward. The results of the evaluation are expressed as index values ​​and assessed using the state of the art as a reference value (100). Higher values ​​are preferred in this evaluation.

[0054] The noise performance rating is based on the magnitude of the external noise during a drive-by, measured according to the tire noise test method specified in ECE R117-02 (ECE Regulation No. 117, Revision 2). In this test, the test vehicle starts moving from a position sufficiently far from a noise measurement section, the engine is stopped near the section, and the vehicle is allowed to coast. The maximum noise level in dB (noise level in a frequency range of 800 Hz to 1200 Hz) in the noise measurement section is then measured at several speeds, determined by dividing a speed range of ±10 km / h from a reference speed into eight or more sections at substantially regular intervals. The maximum noise levels are then averaged to obtain the external noise during a drive-by.The maximum noise level dB is a sound pressure dB(A) measured by an A-characteristic frequency correction circuit using a stationary microphone positioned at an intermediate point in the noise measurement section, 7.5 m from a center line in the vehicle width direction and 1.2 m above the road surface. Pass-by noise is expressed as an index value, with the prior art example assigned as reference (100), and a higher numerical value indicating a lower sound pressure dB and superior noise performance compared to pass-by noise.

[0055] For the pneumatic tires according to examples 1 to 21, the relationships of the groove width G1 of the first main groove 11, the groove width G2 of the second main groove 12, the groove width G3 of the third main groove 13 and the groove width G4 of the fourth main groove 14 are 1.05 ≤ G1 / G3 ≤ 1.25, 1.20 ≤ G2 / G3 ≤ 1.40 and 1.10 ≤ G4 / G3 ≤ 1.30 and furthermore have the relationships G3 < G1 < G2 and G3 < G1 < G4.

[0056] Examples 1 to 21 are set as specified in Tables 1 to 3. In other words, the following tires are produced: a tire in which the groove width G2 is greater than the groove width G4, and a tire in which the groove width G2 is less than the groove width G4; a tire in which, for the width of the outer rib section Ro, the width of the middle rib section Rc, and the width of the inner rib section Ri, the ratio of the maximum rib section width to the minimum rib section width is less than or equal to 1.05, and a tire in which the ratio of the maximum rib section width to the minimum rib section width is greater than 1.05; a tire in which the inner shoulder rib section Si has a circumferential narrow groove, in other words, the first narrow groove 15, and a tire in which the inner shoulder rib section Si does not have a circumferential narrow groove;Tires with a Gs / G3 ratio of 0.10, 0.20 and 0.30; tires with a D2 / D1 ratio of 0.15, 0.20 and 0.30; a tire in which the inner rib section Ri contains the first lug grooves 30, and a tire in which the inner rib section Ri does not contain the first lug grooves 30; tires with a W1 / W2 ratio of 1.00, 0.20, 0.35, 0.50 and 0.60; a tire in which the inner shoulder rib section Si and the outer shoulder rib section So contain the third lug grooves 32 and the fourth lug grooves 33, and a tire in which the inner shoulder rib section Si and the outer shoulder rib section So do not contain the third lug grooves 32 and the fourth lug grooves 33;a tire in which the third lug grooves 32 are connected to the first main groove 11 and in which the fourth lug grooves 33 are connected to the fourth main groove 14, and a tire in which the third lug grooves 32 are not connected to the first main groove 11 and in which the fourth lug grooves 33 are not connected to the fourth main groove 14 (no connection); and a tire in which the outer shoulder rib section So contains sipes, and a tire in which the outer shoulder rib section So does not contain sipes; In all tires, the groove width G1, the groove width G2, and the groove width G3 have the relationship (G2 - G1) / G3 ≥ 0.01.

[0057] In the pneumatic tire according to the prior art example 1, the groove widths G1 to G4 are the same, the outer shoulder rib section So and the inner shoulder rib section Si have a circumferential narrow groove, the inner rib section Ri does not have a circumferential narrow groove, the inner rib section Ri and the outer shoulder rib section So contain lug grooves, and the lug grooves are not connected to the main grooves.

[0058] For comparison, pneumatic tires were manufactured according to Comparison Example 1, Comparison Example 2, and Comparison Example 3. In the pneumatic tire according to Comparison Example 1, the groove widths G1 and G4 vary; the outer shoulder rib section So has a circumferential narrow groove; the inner shoulder rib section Si does not have a circumferential narrow groove; the inner rib section Ri does not have a circumferential narrow groove; the inner shoulder rib section Si and the outer shoulder rib section So contain lug grooves; in the inner shoulder rib section Si, the lug grooves are connected to the main groove, and in the outer shoulder rib section So, the lug grooves are not connected to the main groove. In the pneumatic tire according to Comparison Example 2, the groove widths G1 to G4 have the relationship G3 < G4 < G2 < G1. In the pneumatic tire according to Comparison Example 3, the groove widths G1 to G4 have the relationship G3 < G1 = G2 = G4.

[0059] These pneumatic tires were evaluated using the assessment methods described above with regard to dry steering stability performance, wet steering stability performance, and noise performance. The results are also shown in Tables 1 to 3.

[0060] As shown in Tables 1 to 3, good results were obtained in the following cases with regard to dry steering stability performance, wet steering stability performance, and noise performance: A case in which the relationships 1.05 ≤ G1 / G3 ≤ 1.25, 1.20 ≤ G2 / G3 ≤ 1.40, and 1.10 ≤ G4 / G3 ≤ 1.30 are satisfied, and furthermore, when the relationships G3 < G1 < G2 and G3 < G1 < G4 are satisfied; a case in which the groove width G2 is greater than the groove width G4 (G4 < G2); a case in which, for the width of the outer web section Ro, the width of the central web section Rc, and the width of the inner web section Ri, the ratio of the maximum web section width to the minimum web section width is less than or equal to 1.05; a case in which the inner shoulder bridge section Si contains the first narrow groove 15; a case in which the ratio Gs / G3 0.10 ≤ Gs / G3 ≤ 0.30; a case in which the inner bridge section Ri contains the second narrow groove 16;a case in which the ratio Gr / G3 has the relationship 0.10 ≤ Gr / G3 ≤ 0.30; a case in which the ratio D2 / D1 is greater than or equal to 0.15 and less than or equal to 0.30; a case in which the inner bridge section Ri contains the first lug grooves 30; a case in which the ratio W1 / W2 is in the range of 0.20 ≤ W / / W2 ≤ 0.60; a case in which the inner shoulder bridge section Si and the outer shoulder bridge section So contain the third lug grooves 32 and the fourth lug grooves 33; a case in which the third lug grooves 32 are not connected to the first main groove 11 and in which the fourth lug grooves 33 are not connected to the fourth main groove 14; and a case in which the outer shoulder bridge section So contains lamellae. [Table 1-I] State of the art example 1 Comparative example 1 Example 1 Example 2 Comparative example 2 G1 / G3 1,00 0.8 to 1.1 1,05 1,25 1,30 G2 / G3 1,00 1,00 1,25 1,30 1,25 G4 / G3 1,00 0.8 to 1.1 1,20 1,30 1,20 Maximum web section width / minimum web section width - - 1,00 1,00 1,00 Narrow circumferential groove in the outer shoulder strap section. Yes Yes No No No Narrow circumferential groove in the inner shoulder bridge section Si Yes No No No No Gs / G3 - - - - - Narrow circumferential groove in the inner web section Ri No No No No No Gr / G3 - - - - - D2 / D1 - - - - - Tunnel grooves in the inner bridge section Ri Yes Yes No No No W1 / W2 - - - - - Lug grooves in shoulder bridge sections Si and So Yes Yes No No No Lamellas in the outer shoulder bridge section So No No No No No Connection / no connection with lug grooves No connection Connection / No connection - - - Dry steering stability performance 100 100 103 103 103 Wet steering stability performance 100 100 100 100 100 noise level 100 100 103 103 97 [Table 1-II] Comparative example 3 Example 3 Example 4 Example 5 Example 6 G1 / G3 1,20 1,10 1,10 1,05 1,10 G2 / G3 1,20 1,20 1,40 1,30 1,20 G4 / G3 1,20 1,15 1,20 1,10 1,30 Maximum web section width / minimum web section width 1,00 1,00 1,00 1,00 1,00 Narrow circumferential groove in the outer shoulder strap section. No No No No No Narrow circumferential groove in the inner shoulder bridge section Si No No No No No Gs / G3 - - - - - Narrow circumferential groove in the inner web section Ri No No No No No Gr / G3 - - - - - D2 / D1 - - - - - Tunnel grooves in the inner bridge section Ri No No No No No W1 / W2 - - - - - Lug grooves in shoulder bridge sections Si and So No No No No No Lamellas in the outer shoulder bridge section So No No No No No Connection / no connection with lug grooves Dry steering stability performance 103 103 102 103 103 Wet steering stability performance 100 100 100 100 100 noise level 97 103 102 104 103 [Table 2-I] Example 7 Example 8 Example 9 Example 10 G1 / G3 1,10 1,10 1,20 1,20 G2 / G3 1,25 1,25 1,25 1,25 G4 / G3 1,20 1,20 1,30 1,30 Maximum web section width / minimum web section width 1,00 1,00 1,00 1,05 Narrow circumferential groove in the outer shoulder strap section. No No No No Narrow circumferential groove in the inner shoulder bridge section Si Yes Yes Yes Yes Gs / G3 0,10 0,20 0,30 0,20 Narrow circumferential groove in the inner web section Ri No No No No Gr / G3 - - - - D2 / D1 - - - - Tunnel grooves in the inner bridge section Ri No No No No W1 / W2 - - - - Lug grooves in shoulder bridge sections Si and So No No No No Lamellas in the outer shoulder bridge section So No No No No Connection / no connection with lug grooves Dry steering stability performance 104 105 105 105 Wet steering stability performance 101 100 101 101 noise level 104 105 105 105 [Table 2-II] Example 11 Example 12 Example 13 Example 14 G1 / G3 1,20 1,20 1,20 1,10 G2 / G3 1,25 1,25 1,25 1,25 G4 / G3 1,30 1,30 1,30 1,20 Maximum web section width / minimum web section width 1,10 1,00 1,00 1,00 Narrow circumferential groove in the outer shoulder strap section. No No No No Narrow circumferential groove in the inner shoulder bridge section Si Yes Yes Yes Yes Gs / G3 0,20 0,20 0,20 0,20 Narrow circumferential groove in the inner web section Ri No Yes Yes Yes Gr / G3 - 0,10 0,10 0,20 D2 / D1 - 0,15 0,30 0,20 Tunnel grooves in the inner bridge section Ri No No No Yes W1 / W2 - - - 1,00 Lug grooves in shoulder bridge sections Si and So No No No No Lamellas in the outer shoulder bridge section So No No No No Connection / no connection with lug grooves Dry steering stability performance 104 104 105 105 Wet steering stability performance 101 101 101 101 noise level 104 105 104 105 [Table 3-I] Example 15 Example 16 Example 17 Example 18 G1 / G3 1,10 1,10 1,10 1,10 G2 / G3 1,25 1,25 1,25 1,25 G4 / G3 1,20 1,20 1,20 1,20 Maximum web section width / minimum web section width 1,00 1,00 1,00 1,00 Narrow circumferential groove in the outer shoulder strap section. No No No No Narrow circumferential groove in the inner shoulder bridge section Si Yes Yes Yes Yes Gs / G3 0,20 0,20 0,20 0,20 Narrow circumferential groove in the inner web section Ri Yes Yes Yes Yes Gr / G3 0,20 0,20 0,20 0,20 D2 / D1 0,20 0,20 0,20 0,20 Tunnel grooves in the inner bridge section Ri Yes Yes Yes Yes W1 / W2 0,35 0,20 0,60 0,35 Lug grooves in shoulder bridge sections Si and So No No No Yes Lamellas in the outer shoulder bridge section So No No No No Connection / no connection with lug grooves - - - Connection Dry steering stability performance 105 105 105 105 Wet steering stability performance 103 107 105 105 noise level 105 103 105 105 [Table 3-II] Example 19 Example 20 Example 21 G1 / G3 1,10 1,10 1,20 G2 / G3 1,25 1,25 1,25 G4 / G3 1,20 1,20 1,30 Maximum web section width / minimum web section width 1,00 1,00 1,00 Narrow circumferential groove in the outer shoulder strap section. No No No Narrow circumferential groove in the inner shoulder bridge section Si Yes Yes Yes Gs / G3 0,20 0,20 0,30 Narrow circumferential groove in the inner web section Ri Yes Yes Yes Gr / G3 0,30 0,20 0,20 D2 / D1 0,20 0,20 0,20 Tunnel grooves in the inner bridge section Ri Yes Yes Yes W1 / W2 0,50 0,35 0,35 Lug grooves in shoulder bridge sections Si and So Yes Yes Yes Lamellas in the outer shoulder bridge section So No Yes Yes Connection / no connection with lug grooves Connection No connection No connection Dry steering stability performance 105 105 105 Wet steering stability performance 107 105 107 noise level 103 110 108 List of reference symbols 1 tread section 2 Side wall section 3 bead section 4 Carcass layer 5 bead core 6 bead fillers 7th belt layer 8 Belt cover layer 10 pneumatic tires 11 First main groove 12 Second main groove 13 Third main groove 14 Fourth main groove 15 First narrow groove 16 Second narrow groove 30 First groove 30A First groove section 30B Second groove section 31 Second cleat groove 32 Third groove 33 Fourth cleat groove 34 Fifth groove 35 Sixth groove 36 Seventh groove 40 slats CL tire equatorial plane RC Central Bridge Section Ri Inner Bridge Section Ro Outer Bridge Section Si Inner shoulder bridge section Outer shoulder strap section T Ground contact edge of the tire

Claims

[1] A pneumatic tire having a mounting direction indicating portion that indicates a mounting direction of a tire with respect to a vehicle; and a tread surface in which an outer side and an inner side are asymmetrical in a vehicle width direction with respect to an equatorial plane of the tire; wherein the tread surface includes a first main groove extending in a tire circumferential direction at a position outward from the equatorial plane of the tire in the vehicle width direction, a second main groove extending in the tire circumferential direction at a position closer to the equatorial plane of the tire than the first main groove, a third main groove extending in the tire circumferential direction at a position inward from the equatorial plane of the tire in the vehicle width direction, and a fourth main groove extending in the tire circumferential direction at a position farther from the equatorial plane of the tire than the third main groove; where the relationships 1.05 ≤ G1 / G3 ≤ 1.25, 1.20 ≤ G2 / G3 ≤ 1.40 and 1.10 ≤ G4 / G3 ≤ 1.30 are satisfied; and the relationships G3 < G1 < G2 and G3 < G1 < G4 are fulfilled, where G1 is a groove width of the first main groove, G2 is a groove width of the second main groove, G3 is a groove width of the third main groove, and G4 is a groove width of the fourth main groove. [2] A pneumatic tire according to claim 1, wherein the groove width G2 of the second main groove and the groove width G4 of the fourth main groove have a relationship of G4 < G2. [3] A pneumatic tire according to claim 1 or 2, wherein the groove width G1 of the first main groove, the groove width G2 of the second main groove and the groove width G3 of the third main groove have a relationship of (G2 - G1) / G3 ≥ 0.

01. [4] A pneumatic tire according to any one of claims 1 to 3, wherein for a width of an outer land portion between the first main groove and the second main groove, a width of a middle land portion between the second main groove and the third main groove, and a width of an inner land portion between the third main groove and the fourth main groove, a ratio of a maximum width to a minimum width is less than or equal to 1.

05. [5] A pneumatic tire according to any one of claims 1 to 3, wherein for a width of an outer land portion between the first main groove and the second main groove, a width of a middle land portion between the second main groove and the third main groove, and a width of an inner land portion between the third main groove and the fourth main groove, at least one of the widths is different from the other widths. [6] A pneumatic tire according to any one of claims 1 to 5, further comprising a first narrow groove extending in the tire circumferential direction at a position further inside than the fourth main groove in the vehicle width direction, wherein a groove width Gs of the first narrow groove and the groove width G3 of the third main groove have a relationship of 0.10 ≤ Gs / G3 ≤ 0.

30. [7] A pneumatic tire according to any one of claims 1 to 6, further comprising a second narrow groove provided in the inner land portion and extending in the tire circumferential direction, wherein a groove width Gr of the second narrow groove and the groove width G3 of the third main groove have a relationship of 0.10 ≤ Gr / G3 ≤ 0.

30. [8] A pneumatic tire according to claim 7, wherein in the inner land portion, the second narrow groove is provided at a position where a ratio of a distance from the third main groove to a length of the inner land portion in the vehicle width direction is greater than or equal to 0.15 and less than or equal to 0.

30. [9] A pneumatic tire according to claim 8, further comprising a first lug groove opening at a first end to the second narrow groove and opening at a second end to the fourth main groove. [10] A pneumatic tire according to claim 9, wherein the first lug groove has a groove width that varies between the first end and the second end, and a relationship between a groove width W1 at the first end side and a groove width W2 at the second end side is in the range of 0.20 ≤ W1 / W2 ≤ 0.

60. [11] A pneumatic tire according to any one of claims 1 to 10, further comprising a second lug groove opening to the first main groove at a first end and extending outward in the vehicle width direction at a second end; and a sipe connected to the second end of the second lug groove at a first end and extending outward in the vehicle width direction at a second end. [12] A pneumatic tire according to any one of claims 1 to 11, further comprising a third lug groove extending in the vehicle width direction from a position further outward than the first main groove in the vehicle width direction; and a fourth lug groove extending in the vehicle width direction from a position further inward than the fourth main groove in the vehicle width direction, wherein the third lug groove does not open to the first main groove and the fourth lug groove does not open to the fourth main groove. [13] A pneumatic tire according to any one of claims 1 to 12, wherein a distance from the equatorial plane of the tire to the second main groove is shorter than a distance from the equatorial plane of the tire to the third main groove.

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