Pneumatic tires

Abstract

To provide a pneumatic tire improved with well balance in steering stability, noise reduction performance and drainage performance.SOLUTION: A pneumatic tire is configured so that: inner intermediate lug grooves are formed in an inner intermediate land part, and outer intermediate lug grooves are formed in an outer intermediate land part; a length L1 of the inner intermediate lug groove and a length L2 of the outer intermediate lug groove satisfy a relation of L1>L2; a distance W1 from a tire equator to an inner shoulder major groove, a distance W2 from the tire equator to an inner center major groove, a distance W3 from the tire equator to an outer center major groove and a distance W4 from the tire equator to an outer shoulder major groove satisfy relations of 0.58≤W1 / Wi≤0.62, 0.20≤W2 / Wi≤0.24, 0.15≤W3 / Wo≤0.19, and 0.53≤W4 / Wo≤0.57 with respect to distances Wi, Wo from the tire equator to ground contact ends; and the total value of a groove width WG1 of the inner shoulder major groove and a groove width WG2 of the inner center major groove is larger than the total value of a groove width WG3 of the outer center major groove and a groove width WG4 of the outer shoulder major groove.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire having four main grooves in a tread portion, and more specifically, to a pneumatic tire that enables improvements in driving stability, noise performance, and drainage performance in a well-balanced manner. [Background technology]

[0002] In pneumatic tires, various proposals have been made to ensure drainage performance by adopting a tread pattern in which four main grooves extending circumferentially of the tire are formed in the tread portion and a plurality of lug grooves are formed in the land areas partitioned by these main grooves (see, for example, Patent Documents 1 to 3).

[0003] However, when the groove area of ​​the main groove or the lug groove is increased, the drainage performance can be improved, but there is a problem that the driving stability and noise performance are deteriorated. Therefore, it is not easy to achieve high levels of driving stability, noise performance, and drainage performance at the same time, and further improvements are desired. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-51834 A [Patent Document 2] JP 2019-1406 A [Patent Document 3] Patent No. 5413500 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a pneumatic tire which enables improvements in steering stability, noise performance and drainage performance in a well-balanced manner. [Means for solving the problem]

[0006] In order to achieve the above object, a pneumatic tire of the present invention includes a tread portion extending in a circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the radially inner sides of the sidewall portions, and the pneumatic tire has a mounting direction indicator portion that indicates a mounting direction relative to a vehicle, Four main grooves extending in the tire circumferential direction are formed in the tread portion, the four main grooves including an inner center main groove located on the vehicle inner side of the tire equator when mounted on the vehicle, an outer center main groove located on the vehicle outer side of the tire equator when mounted on the vehicle, an inner shoulder main groove located on the vehicle inner side of the inner center main groove when mounted on the vehicle, and an outer shoulder main groove located on the vehicle outer side of the outer center main groove when mounted on the vehicle, five rows of land portions are defined by the four main grooves, the five rows of land portions including a center land portion defined between the inner center main groove and the outer center main groove, an inner intermediate land portion defined between the inner center main groove and the inner shoulder main groove, an outer intermediate land portion defined between the outer center main groove and the outer shoulder main groove, an inner shoulder land portion defined on the inner side of the vehicle than the inner shoulder main groove, and an outer shoulder land portion defined on the outer side of the vehicle than the outer shoulder main groove, a plurality of inner intermediate lug grooves are formed at intervals in the tire circumferential direction in the inner intermediate land portion, the inner intermediate lug grooves extending in the tire width direction, one end of which is connected to the inner center main groove and the other end of which is terminated within the inner intermediate land portion, while a plurality of outer intermediate lug grooves are formed at intervals in the tire circumferential direction in the outer intermediate land portion, the inner intermediate lug grooves extending in the tire width direction, one end of which is connected to the outer shoulder main groove and the other end of which is terminated within the outer intermediate land portion, and a length L1 of the inner intermediate lug groove and a length L2 of the outer intermediate lug groove satisfy a relationship of L1>L2; a distance W1 from the tire equator to the center position of the inner shoulder main groove, a distance W2 from the tire equator to the center position of the inner center main groove, a distance W3 from the tire equator to the center position of the outer center main groove, and a distance W4 from the tire equator to the center position of the outer shoulder main groove, relative to distances Wi and Wo from the tire equator to the vehicle inner and vehicle outer ground contact edges, respectively, satisfy the relationships of 0.58≦W1 / Wi≦0.62, 0.20≦W2 / Wi≦0.24, 0.15≦W3 / Wo≦0.19, and 0.53≦W4 / Wo≦0.57, The sum of the groove width WG1 of the inner shoulder main groove and the groove width WG2 of the inner center main groove is greater than the sum of the groove width WG3 of the outer center main groove and the groove width WG4 of the outer shoulder main groove. Effect of the Invention

[0007] In the present invention, in a pneumatic tire in which the mounting direction relative to a vehicle is specified, W1 / Wi, W2 / Wi, W3 / Wo, and W4 / Wo are specified as above, and the four main grooves are moved toward the inside of the vehicle when mounted on the vehicle, thereby reducing noise outside the vehicle and improving drainage performance. Also, by making the total value of the groove width WG1 of the inner shoulder main groove and the groove width WG2 of the inner center main groove larger than the total value of the groove width WG3 of the outer center main groove and the groove width WG4 of the outer shoulder main groove, drainage performance can be improved without deteriorating noise performance. Furthermore, by making the total value of the groove width WG1 of the inner shoulder main groove and the groove width WG2 of the inner center main groove larger than the total value of the groove width WG3 of the outer center main groove and the groove width WG4 of the outer shoulder main groove, in addition to making the length L1 of the inner intermediate lug groove larger than the length L2 of the outer intermediate lug groove, the rigidity of the outer side portion of the tread portion where a large lateral force acts is made larger than the rigidity of the inner side portion of the tread portion, thereby improving steering stability on dry and wet road surfaces. As a result, it is possible to improve the driving stability, noise performance and drainage performance to a higher level.

[0008] In the present invention, it is preferable that the central land portion has a plurality of center lug grooves formed at intervals in the tire circumferential direction, each of which extends in the tire width direction, has one end connected to the inner center main groove, and has the other end terminated within the central land portion. By disposing the non-through center lug grooves in the central land portion, it is possible to improve drainage performance without impairing steering stability.

[0009] In particular, it is preferable that the other end of the center lug groove terminates within the center land portion without crossing the tire equator. By arranging the center lug groove so as not to cross the tire equator, it is possible to ensure sufficient rigidity of the center land portion and improve drainage performance without deteriorating steering stability.

[0010] In addition, it is preferable that the central land portion has a plurality of center sipes formed at intervals in the tire circumferential direction, the center sipes extending in the tire width direction, one end of which is connected to the outer center main groove, and the other end of which is terminated within the central land portion without crossing the tire equator. By arranging the center sipes so as not to cross the tire equator, it is possible to sufficiently secure the rigidity of the central land portion and improve drainage performance without deteriorating noise performance or driving stability.

[0011] The width Wr1 of the inner intermediate land portion and the length L1 of the inner intermediate lug groove preferably satisfy the relationship 0.6≦L1 / Wr1≦0.7. The width Wr2 of the outer intermediate land portion and the length L2 of the outer intermediate lug groove preferably satisfy the relationship 0.4≦L2 / Wr2≦0.5. The width Wr3 of the center land portion and the length L3 of the center lug groove preferably satisfy the relationship 0.3≦L3 / Wr3≦0.4. By optimizing the length L1 of the inner intermediate lug groove, the length L2 of the outer intermediate lug groove, or the length L3 of the center lug groove, it is possible to improve the driving stability, noise performance, and drainage performance in a well-balanced manner.

[0012] The inclination angle θ1 of the inner intermediate lug groove on the acute side relative to the tire circumferential direction is preferably smaller than the inclination angle θ2 of the outer intermediate lug groove on the acute side relative to the tire circumferential direction. By making the inclination angle θ1 of the inner intermediate lug groove smaller than the inclination angle θ2 of the outer intermediate lug groove in this way, it is possible to ensure the rigidity of the inner intermediate land portion while maintaining good drainage performance. As a result, it is possible to improve the steering stability on dry roads and on wet roads in a well-balanced manner.

[0013] The groove walls of the inner shoulder main groove and the outer center main groove on the vehicle outer side preferably have a zigzag chamfered edge portion. By having the groove walls of the inner shoulder main groove and the outer center main groove on the vehicle outer side have a zigzag chamfered edge portion, the initial groove area can be secured without increasing noise, and drainage performance can be improved.

[0014] The inner intermediate lug groove preferably has an inclined portion that starts from its opening end at 50% to 65% of the length L1 and gradually becomes shallower toward the terminal end. The outer intermediate lug groove preferably has an inclined portion that starts from its opening end at 35% to 50% of the length L2 and gradually becomes shallower toward the terminal end. The center lug groove preferably has an inclined portion that starts from its opening end at 25% to 40% of the length L3 and gradually becomes shallower toward the terminal end. By providing such an inclined portion, it is possible to avoid a decrease in the rigidity of each land portion, and therefore it is possible to improve drainage performance without deteriorating steering stability.

[0015] In the present invention, the contact area of ​​the tread portion is specified based on the contact width in the axial direction of the tire measured when the tire is mounted on a standard rim, inflated to the standard internal pressure, placed vertically on a flat surface, and subjected to a standard load. The contact edge is the outermost position in the axial direction of the tire in the contact area. The "standard rim" is a rim that is determined for each tire by a standard system including the standard on which the tire is based, for example, a standard rim for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO. The "standard internal pressure" is an air pressure that corresponds to the maximum load capacity determined for each tire by each standard in the standard system including the standard on which the tire is based. The "standard load" is a load that corresponds to 80% of the maximum load capacity determined for each tire by each standard in the standard system including the standard on which the tire is based. [Brief description of the drawings]

[0016] [Figure 1] 1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. [Diagram 3] 2 is a contour diagram showing the contour of the pneumatic tire of FIG. 1 at a meridian cross section of a tread portion. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the configuration of the present invention will be described in detail with reference to the attached drawings. Figures 1 to 3 show a pneumatic tire according to an embodiment of the present invention. This pneumatic tire is a tire in which the mounting direction of the front and back of the tire when mounted on a vehicle is specified. In Figures 1 to 3, IN is the inside of the vehicle when mounted on the vehicle, OUT is the outside of the vehicle when mounted on the vehicle, Ei is the ground contact edge on the inside of the vehicle, Eo is the ground contact edge on the outside of the vehicle, and TCW is the ground contact width.

[0018] As shown in Fig. 1, the pneumatic tire of this embodiment includes a tread portion 1 extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged on the tire radially inward side of the sidewall portions 2. For example, at least the sidewall portion 2 on the outer side of the vehicle is formed with a mounting direction display portion 2A indicating the mounting direction relative to the vehicle. The mounting direction display portion 2A displays, for example, "OUTSIDE" along the tire circumferential direction on the outer side of the vehicle, and displays, for example, "INSIDE" along the tire circumferential direction on the inner side of the vehicle.

[0019] A carcass layer 4 is fitted between a pair of bead portions 3, 3. This carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around a bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5.

[0020] On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to, for example, a range of 10° to 40°. As the reinforcing cords of the belt layers 7, steel cords are preferably used. On the outer peripheral side of the belt layers 7, at least one belt cover layer 8 is arranged in which reinforcing cords are arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction for the purpose of improving high-speed durability. As the reinforcing cords of the belt cover layer 8, organic fiber cords such as nylon and aramid are preferably used.

[0021] It should be noted that the above-described tire internal structure shows a typical example of a pneumatic tire, but is not limited thereto.

[0022] As shown in Fig. 2, the tread portion 1 is formed with four main grooves 11 extending in the tire circumferential direction. The four main grooves 11 include an inner center main groove 11B located on the vehicle inner side of the tire equator CL when mounted on the vehicle, an outer center main groove 11C located on the vehicle outer side of the tire equator CL when mounted on the vehicle, an inner shoulder main groove 11A located on the vehicle inner side of the inner center main groove 11B when mounted on the vehicle, and an outer shoulder main groove 11D located on the vehicle outer side of the outer center main groove 11C when mounted on the vehicle. The main grooves 11 have a groove width in the range of 6.5 mm to 12.0 mm, a groove depth in the range of 6.5 mm to 8.5 mm, and are equipped with a wear indicator.

[0023] These four main grooves 11 define five rows of land portions 12 in the tread portion 1. The five rows of land portions 12 include a center land portion 12C defined between the inner center main groove 11B and the outer center main groove 11C, an inner intermediate land portion 12B defined between the inner center main groove 11B and the inner shoulder main groove 11A, an outer intermediate land portion 12D defined between the outer center main groove 11C and the outer shoulder main groove 11D, an inner shoulder land portion 12A defined on the inner side of the vehicle than the inner shoulder main groove 11A, and an outer shoulder land portion 12E defined on the outer side of the vehicle than the outer shoulder main groove 11D.

[0024] In the inner shoulder land portion 12A, a plurality of inner shoulder lug grooves 13A are formed at intervals in the tire circumferential direction, each of which extends in the tire width direction, has one end extending toward the vehicle inner side of the vehicle inner ground contact edge Ei, and the other end terminating within the inner shoulder land portion 12A. In addition, in the inner shoulder land portion 12A, a plurality of inner shoulder sipes 14A are formed at intervals in the tire circumferential direction, each of which extends in the tire width direction, has one end communicating with the inner shoulder main groove 11A, and the other end terminating within the inner shoulder land portion 12A.

[0025] In the inner intermediate land portion 12B, a plurality of inner intermediate lug grooves 13B are formed at intervals in the tire circumferential direction, each of which extends in the tire width direction, has one end connected to the inner center main groove 11B, and the other end terminates within the inner intermediate land portion 12B. In addition, a zigzag-chamfered edge portion 16B is formed on the groove wall on the vehicle outer side of the inner shoulder main groove 11A (i.e., the side wall on the vehicle inner side of the inner intermediate land portion 12B).

[0026] In the center land portion 12C, a plurality of center lug grooves 13C are formed at intervals in the tire circumferential direction, each extending in the tire width direction, one end of which is connected to the inner center main groove 11B, and the other end of which is terminated within the center land portion 12C. In addition, in the center land portion 12C, a plurality of center sipes 14C are formed at intervals in the tire circumferential direction, each extending in the tire width direction, one end of which is connected to the outer center main groove 11C, and the other end of which is terminated within the center land portion 12C.

[0027] In the outer intermediate land portion 12D, a plurality of outer intermediate lug grooves 13D are formed at intervals in the tire circumferential direction, each of which extends in the tire width direction, has one end connected to the outer shoulder main groove 11D, and the other end terminates within the outer intermediate land portion 12D. In addition, a zigzag chamfered edge portion 16D is formed in the groove wall on the outer side of the vehicle of the outer center main groove 11C (i.e., the side wall on the inner side of the vehicle of the outer intermediate land portion 12D).

[0028] In the outer shoulder land portion 12E, a plurality of outer shoulder lug grooves 13E are formed at intervals in the tire circumferential direction, each of which extends in the tire width direction, has one end extending further outboard than the outer ground contact edge Eo of the vehicle, and the other end terminating within the outer shoulder land portion 12E. In the outer shoulder land portion 12E, a circumferential auxiliary groove 15E is formed, each of which extends in the tire circumferential direction and connects the outer shoulder lug grooves 13E to each other. In addition, in the outer shoulder land portion 12E, a plurality of outer shoulder sipes 14D are formed at intervals in the tire circumferential direction, each of which extends in the tire width direction, has one end communicating with the outer shoulder main groove 11D, and the other end communicating with the circumferential auxiliary groove 15E.

[0029] In the above pneumatic tire, the length L1 of the inner intermediate lug groove 13B and the length L2 of the outer intermediate lug groove 13D satisfy the relationship L1>L2. The lengths L1 and L2 are measured in the tire width direction. By making the length L1 of the inner intermediate lug groove 13B longer than the length L2 of the outer intermediate lug groove 13D in this manner, the rigidity of the vehicle outer side portion of the tread portion 1 (outer intermediate land portion 12D) where a large lateral force acts is made greater than the rigidity of the vehicle inner side portion of the tread portion 1 (inner intermediate land portion 12B), thereby improving the steering stability on dry and wet road surfaces.

[0030] In the above pneumatic tire, the distance W1 from the tire equator CL to the center position of the inner shoulder main groove 11A, the distance W2 from the tire equator CL to the center position of the inner center main groove 11B, the distance W3 from the tire equator CL to the center position of the outer center main groove 11C, and the distance W4 from the tire equator CL to the center position of the outer shoulder main groove 11D satisfy the relationships 0.58≦W1 / Wi≦0.62, 0.20≦W2 / Wi≦0.24, 0.15≦W3 / Wo≦0.19, and 0.53≦W4 / Wo≦0.57 with respect to the distances Wi and Wo from the tire equator CL to the vehicle inner and outer ground contact edges Ei and Eo. Each of the distances Wi and Wo from the tire equator CL to the vehicle inner and outer ground contact edges Ei and Eo corresponds to TCW / 2. The center positions of the inboard shoulder main groove 11A, the inboard center main groove 11B, the outboard center main groove 11C and the outboard shoulder main groove 11D are the center positions in the groove width direction, which are the centers of the groove portions excluding the chamfered portions.

[0031] In a pneumatic tire with a specified mounting direction on a vehicle, by defining W1 / Wi, W2 / Wi, W3 / Wo, and W4 / Wo as described above and by moving the four main grooves toward the inside of the vehicle when mounted on the vehicle, it is possible to reduce noise outside the vehicle and improve drainage performance. Here, if the center positions of the inner shoulder main groove 11A, the inner center main groove 11B, the outer center main groove 11C, and the outer shoulder main groove 11D are out of the above range, it becomes difficult to achieve both noise performance and drainage performance.

[0032] In the above pneumatic tire, the total value (WG1+WG2) of the groove width WG1 of the inner shoulder main groove 11A and the groove width WG2 of the inner center main groove 11B is set to be larger than the total value (WG3+WG4) of the groove width WG3 of the outer center main groove 11C and the groove width WG4 of the outer shoulder main groove 11D. This improves drainage performance without deteriorating noise performance. In addition, by making the total value of the groove width WG1 of the inner shoulder main groove 11A and the groove width WG2 of the inner center main groove 11B larger than the total value of the groove width WG3 of the outer center main groove 11C and the groove width WG4 of the outer shoulder main groove 11D, the rigidity of the outer side portion of the tread portion 1, where a large lateral force acts, is made larger than the rigidity of the inner side portion of the tread portion 1, thereby improving steering stability on dry road surfaces and wet road surfaces. In particular, it is preferable to satisfy the relationship WG1≧WG2>WG3≧WG4.

[0033] In the above pneumatic tire, it is preferable that the center land portion 12C has a plurality of center lug grooves 13C formed at intervals in the tire circumferential direction, the center lug grooves 13C extending in the tire width direction, one end of which is connected to the inner center main groove 11B, and the other end of which is terminated within the center land portion 12C. By arranging the non-penetrating center lug grooves 13C in the center land portion 12C in this manner, it is possible to improve drainage performance without impairing steering stability.

[0034] When providing the center lug groove 13C, it is preferable that the other end of the center lug groove 13C terminates within the center land portion 12C without crossing the tire equator CL. By arranging the center lug groove 13C so as not to cross the tire equator CL, it is possible to ensure sufficient rigidity of the center land portion 12C and improve drainage performance without deteriorating steering stability.

[0035] In the above pneumatic tire, it is preferable that the central land portion 12C has a plurality of central sipes 14C formed at intervals in the tire circumferential direction, the central sipes 14C extending in the tire width direction, one end of which communicates with the outer central main groove 11C, and the other end of which terminates within the central land portion 12C without crossing the tire equator CL. By arranging the central sipes 14C so as not to cross the tire equator CL, it is possible to sufficiently secure the rigidity of the central land portion 12C and improve the drainage performance without deteriorating the noise performance or the driving stability.

[0036] In the above pneumatic tire, the width Wr1 of the inner intermediate land portion 12B and the length L1 of the inner intermediate lug groove 13B preferably satisfy the relationship 0.6≦L1 / Wr1≦0.7. By optimizing the length L1 of the inner intermediate lug groove 13B, it is possible to improve the driving stability, noise performance, and drainage performance in a well-balanced manner. Here, if the value of L1 / Wr1 is smaller than 0.6, the improvement effect of drainage performance is reduced, and conversely, if it is larger than 0.7, the improvement effect of driving stability is reduced due to the reduction in rigidity of the inner intermediate land portion 12B, and the improvement effect of noise performance is also reduced.

[0037] In the above pneumatic tire, the width Wr2 of the outer intermediate land portion 12D and the length L2 of the outer intermediate lug groove 13D preferably satisfy the relationship 0.4≦L2 / Wr2≦0.5. By optimizing the length L2 of the outer intermediate lug groove 13D, it is possible to improve the driving stability, noise performance, and drainage performance in a well-balanced manner. Here, if the value of L2 / Wr2 is smaller than 0.4, the improvement effect of drainage performance is reduced, and conversely, if it is larger than 0.5, the improvement effect of driving stability is reduced due to the reduction in the rigidity of the outer intermediate land portion 12D, and the improvement effect of noise performance is also reduced.

[0038] In the above pneumatic tire, the width Wr3 of the center land portion 12C and the length L3 of the center lug groove 13C preferably satisfy the relationship 0.3≦L3 / Wr3≦0.4. By optimizing the length L3 of the center lug groove 13C, it is possible to improve the driving stability, noise performance, and drainage performance in a well-balanced manner. Here, if the value of L3 / Wr3 is smaller than 0.3, the improvement effect of drainage performance is reduced, and conversely, if it is larger than 0.4, the improvement effect of driving stability is reduced due to the reduction in the rigidity of the center land portion 12C, and the improvement effect of noise performance is also reduced.

[0039] In the above pneumatic tire, the inclination angle θ1 of the inner intermediate lug groove 13B on the acute angle side with respect to the tire circumferential direction is preferably set smaller than the inclination angle θ2 of the outer intermediate lug groove 13D on the acute angle side with respect to the tire circumferential direction. The inclination angle θ1 is the angle that a straight line connecting the center position of the opening end of the inner intermediate lug groove 13B and the center position of the terminal end makes with respect to the tire circumferential direction, and the inclination angle θ2 is the angle that a straight line connecting the center position of the opening end of the outer intermediate lug groove 13D and the center position of the terminal end makes with respect to the tire circumferential direction. By making the inclination angle θ1 of the inner intermediate lug groove 13B smaller than the inclination angle θ2 of the outer intermediate lug groove 13D in this way, the rigidity of the inner intermediate land portion 13B can be ensured while maintaining good drainage performance. As a result, the steering stability on dry road surfaces and the steering stability on wet road surfaces can be improved in a well-balanced manner. In particular, it is preferable that the inclination angle θ1 of the inner intermediate lug groove 13B is set in the range of 65° to 71°, and the inclination angle θ2 of the outer intermediate lug groove 13D is set in the range of 72° to 78°.

[0040] In the above pneumatic tire, it is preferable that the groove walls of the inner shoulder main groove 11A and the outer center main groove 11C on the vehicle outer side are respectively formed with zigzag chamfered edges 16B, 16D. By having the zigzag chamfered edges 16B, 16D on the groove walls of the inner shoulder main groove 11A and the outer center main groove 11C on the vehicle outer side, it is possible to secure the initial groove area without increasing noise and improve drainage performance.

[0041] In the above pneumatic tire, as shown in FIG. 3, the inner intermediate lug groove 13B, the center lug groove 13C, and the outer intermediate lug groove 13D have inclined portions 17B, 17C, and 17D that are inclined so that the groove depth gradually becomes shallower from the longitudinal center toward the terminal end. More specifically, the inner intermediate lug groove 13B has a groove depth gradually shallower from a position that is a distance L1' equivalent to 50% to 65% of the length L1 from its opening end toward the terminal end. The outer intermediate lug groove 13D has a groove depth gradually shallower from a position that is a distance L2' equivalent to 35% to 50% of the length L2 from its opening end toward the terminal end. The center lug groove 13C has a groove depth gradually shallower from a position that is a distance L3' equivalent to 25% to 40% of the length L3 from its opening end toward the terminal end. By providing such inclined portions 17B, 17C, 17D, it is possible to avoid a decrease in rigidity of the inner intermediate lug groove 13B, the center lug groove 13C, or the outer intermediate lug groove 13D, and therefore it is possible to improve drainage performance without deteriorating steering stability. Here, if the distances L1', L2', L3' are too small, the effect of improving drainage performance is reduced, and conversely, if they are too large, the effect of improving steering stability is reduced. EXAMPLES

[0042] In a pneumatic tire having a tire size of 215 / 55R17 94V and including a tread portion, a pair of sidewall portions, and a pair of bead portions, and having a mounting direction indicator portion that indicates the mounting direction relative to a vehicle, four main grooves extending in the tire circumferential direction are formed in the tread portion, and five rows of land portions are defined by the four main grooves, and lug grooves and sipes are formed in these land portions. Tires of a conventional example, comparative examples 1 to 3, and examples 1 to 8 were manufactured as shown in FIG. 2 .

[0043] In the conventional example, comparative examples 1 to 3, and examples 1 to 8, the distances Wi and Wo from the tire equator to the ground contact edge, the length L1 of the inner intermediate lug groove, the length L2 of the outer intermediate lug groove, the length L3 of the center lug groove, the distance W1 from the tire equator to the center position of the inner shoulder main groove, the distance W2 from the tire equator to the center position of the inner center main groove, the distance W3 from the tire equator to the center position of the outer center main groove, the distance W4 from the tire equator to the center position of the outer shoulder main groove, W1 / Wi, W2 / Wi, W3 / Wo, W4 / Wo, the groove width WG1 of the inner shoulder main groove and the groove width WG2 of the inner center main groove The total groove width WG2 of the outer center main groove (WG1+WG2), the total groove width WG3 of the outer center main groove and the groove width WG4 of the outer shoulder main groove (WG3+WG4), the end position of the non-through center lug groove, the presence or absence of a non-through center sipe, the width Wr1 of the inner intermediate land portion, the width Wr2 of the outer intermediate land portion, the width Wr3 of the center land portion, L1 / Wr1, L2 / Wr2, L3 / Wr3, the inclination angle θ1 of the inner intermediate lug groove, the inclination angle θ2 of the outer intermediate lug groove, the presence or absence of a zigzag chamfer on the groove wall on the outer side of the vehicle of the inner shoulder main groove and the outer center main groove, the start position L1' of the inclined portion of the inner intermediate lug groove, the start position L2' of the inclined portion of the outer intermediate lug groove, and the start position L3' of the inclined portion of the center lug groove, L1' / L1, L2' / L2, and L3' / L3 were set as shown in Tables 1 and 2. Regarding the termination position of the non-through center lug groove, if the termination is on the tire equator, it is rated as "A", and if the termination is in a position that does not cross the tire equator, it is rated as "B".

[0044] These test tires were evaluated for driving stability on dry roads, driving stability on wet roads, and noise performance by the following test methods. The results are shown in Table 1.

[0045] Stability on dry roads: Each test tire was mounted on a wheel with a rim size of 17x7J and installed on a passenger car with an engine displacement of 2500cc, and the air pressure (F / R) after warming up was set to 230kPa / 220kPa. A sensory evaluation was conducted by a test driver while driving on a dry road surface. The evaluation results were expressed as an index with the conventional example being 100. The higher the index value, the better the handling stability on dry road surfaces.

[0046] Stability on wet roads: Each test tire was mounted on a wheel with a rim size of 17x7J and installed on a passenger vehicle with an engine displacement of 2500cc, and the air pressure (F / R) after warming up was set to 230kPa / 220kPa. A sensory evaluation was conducted by a test driver while driving on a wet road surface. The evaluation results were expressed as an index with the conventional example being 100. The higher the index value, the better the handling stability on wet road surfaces.

[0047] Noise Performance: Each test tire was mounted on a wheel with a rim size of 17x7J and fitted to a passenger vehicle with an engine displacement of 2500cc, and the air pressure (F / R) after warm-up was set to 230kPa / 220kPa, and an external noise measurement test was carried out in accordance with ECE R117 to measure the external noise. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional example being set at 100. The higher the index value, the less external noise there is and the better the noise performance.

[0048] [Table 1]

[0049] [Table 2]

[0050] As can be seen from Tables 1 and 2, the tires of Examples 1 to 7 were generally good in terms of steering stability on dry roads, steering stability on wet roads, and noise performance in comparison with the conventional tires. In contrast, in Comparative Example 1, the length L1 of the inner middle lug groove was smaller than the length L2 of the outer middle lug groove, so the effect of improving steering stability on dry roads and wet roads was insufficient. In Comparative Example 2, the four main grooves were moved toward the outer side of the vehicle when mounted on the vehicle, so not only did the noise performance deteriorate, but the steering stability on wet roads also deteriorated. In Comparative Example 3, the total value (WG1+WG2) of the groove width WG1 of the inner shoulder main groove and the groove width WG2 of the inner center main groove was smaller than the total value (WG3+WG4) of the groove width WG3 of the outer center main groove and the groove width WG4 of the outer shoulder main groove, so not only did the noise performance deteriorate, but the steering stability on dry roads and wet roads also deteriorated. [Explanation of symbols]

[0051] 1 Tread section 2 Sidewall 3 Bead section 11,11A,11B,11C,11D Main groove 12,12A,12B,12C,12D,12E Land 13A, 13B, 13C, 13D, 13E Lug groove 14A, 14C, 14E Sipe 15E Circumferential auxiliary groove 16B, 16D Edge section 17B,17C,17D Slope section

Claims

1. A pneumatic tire includes a tread portion extending in a circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the tire radially inward side of the sidewall portions, the pneumatic tire having a mounting direction indicator portion that indicates a mounting direction relative to a vehicle, Four main grooves extending in the tire circumferential direction are formed in the tread portion, the four main grooves including an inner center main groove located on the vehicle inner side of the tire equator when mounted on the vehicle, an outer center main groove located on the vehicle outer side of the tire equator when mounted on the vehicle, an inner shoulder main groove located on the vehicle inner side of the inner center main groove when mounted on the vehicle, and an outer shoulder main groove located on the vehicle outer side of the outer center main groove when mounted on the vehicle, five rows of land portions are defined by the four main grooves, the five rows of land portions including a center land portion defined between the inner center main groove and the outer center main groove, an inner intermediate land portion defined between the inner center main groove and the inner shoulder main groove, an outer intermediate land portion defined between the outer center main groove and the outer shoulder main groove, an inner shoulder land portion defined on the inner side of the vehicle than the inner shoulder main groove, and an outer shoulder land portion defined on the outer side of the vehicle than the outer shoulder main groove, a plurality of inner intermediate lug grooves are formed in the inner intermediate land portion at intervals in the tire circumferential direction, the inner intermediate lug grooves extending in the tire width direction, one end of which is connected to the inner center main groove and the other end of which is terminated within the inner intermediate land portion, while a plurality of outer intermediate lug grooves are formed in the outer intermediate land portion at intervals in the tire circumferential direction, the outer intermediate land portion at intervals in the tire circumferential direction, the outer intermediate land portion at intervals in the tire circumferential direction, the inner intermediate lug groove length L1 and the outer intermediate lug groove length L2 satisfy the relationship L1>L2, a distance W1 from the tire equator to the center position of the inner shoulder main groove, a distance W2 from the tire equator to the center position of the inner center main groove, a distance W3 from the tire equator to the center position of the outer center main groove, and a distance W4 from the tire equator to the center position of the outer shoulder main groove, relative to distances Wi, Wo from the tire equator to the vehicle-inner and vehicle-outer ground contact edges, satisfy the relationships: 0.58≦W1 / Wi≦0.62, 0.20≦W2 / Wi≦0.24, 0.15≦W3 / Wo≦0.19, and 0.53≦W4 / Wo≦0.57, A pneumatic tire characterized in that a sum of a groove width WG1 of the inner shoulder main groove and a groove width WG2 of the inner center main groove is greater than a sum of a groove width WG3 of the outer center main groove and a groove width WG4 of the outer shoulder main groove.

2. 2. The pneumatic tire according to claim 1, characterized in that a plurality of center lug grooves are formed in the center land portion at intervals in the tire circumferential direction, the center lug grooves extending in the tire width direction, one end of which communicates with the inner center main groove, and the other end of which terminates within the center land portion.

3. 3. The pneumatic tire according to claim 2, wherein the other end of the center lug groove terminates within the center land portion without crossing the tire equator.

4. The pneumatic tire according to any one of claims 1 to 3, characterized in that the center land portion is formed with a plurality of center sipes spaced apart in the tire circumferential direction, the center sipes extending in the tire width direction, one end of which is connected to the outer center main groove, and the other end of which is terminated within the center land portion without crossing the tire equator.

5. The pneumatic tire according to any one of claims 1 to 4, characterized in that a width Wr1 of the inner intermediate land portion and a length L1 of the inner intermediate lug groove satisfy the relationship 0.6≦L1 / Wr1≦0.

7.

6. The pneumatic tire according to any one of claims 1 to 5, characterized in that a width Wr2 of the outer intermediate land portion and a length L2 of the outer intermediate lug groove satisfy the relationship: 0.4≦L2 / Wr2≦0.

5.

7. 4. The pneumatic tire according to claim 2, wherein a width Wr3 of the central land portion and a length L3 of the central lug groove satisfy a relationship of 0.3≦L3 / Wr3≦0.

4.

8. The pneumatic tire according to any one of claims 1 to 7, characterized in that an inclination angle θ1 on the acute angle side with respect to the tire circumferential direction of the inner intermediate lug groove is smaller than an inclination angle θ2 on the acute angle side with respect to the tire circumferential direction of the outer intermediate lug groove.

9. The pneumatic tire according to any one of claims 1 to 8, characterized in that the groove walls of the inboard shoulder main groove and the outboard center main groove on the vehicle outer side have zigzag chamfered edges.

10. The pneumatic tire according to any one of claims 1 to 9, characterized in that the inner intermediate lug groove has an inclined portion that inclines so that the groove depth gradually becomes shallower from a position of 50% to 65% of the length L1 toward the terminal end side, starting from the opening end of the inner intermediate lug groove.

11. The pneumatic tire according to any one of claims 1 to 10, characterized in that the outer intermediate lug groove has an inclined portion that inclines so that the groove depth gradually becomes shallower from a position of 35% to 50% of the length L2 toward the terminal end side, starting from the open end of the outer intermediate lug groove.

12. The pneumatic tire according to claim 2, 3 or 7, characterized in that the center lug groove has an inclined portion that inclines so that the groove depth gradually becomes shallower from a position that is 25% to 40% of the length L3 starting from the opening end of the center lug groove toward the terminal end.

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