pneumatic tires

Abstract

We provide a pneumatic tire that improves handling stability on dry surfaces while simultaneously enhancing handling stability on wet surfaces and reducing external noise. [Solution] Four main grooves 10 extending in the circumferential direction of the tire are formed in the tread portion 1, and these main grooves 10 divide the land portion 20 into five rows, and the four main grooves 10 include a pair of center main grooves 12, 13 and a pair of shoulder main grooves 11, 14 located on the outside in the tire width direction, one of the pair of center main grooves 12, 13 is zigzag shaped, and in at least one row of the land portion 20 of the five rows of land portion 20, a plurality of lug grooves 40 are formed, with at least one end terminating within the land portion 20 and extending in the tire width direction, and of the groove portions on both sides of the lug groove 40 divided at the groove width center position, the groove volume SA of one side of the groove portion is smaller than the groove volume SB of the other side, and the relationship between groove volume SA and groove volume SB satisfies SA / SB ≤ 0.95.

Description

TECHNICAL FIELD

[0001] The present invention relates to a pneumatic tire that enables improved steering stability on dry road surfaces while achieving both enhanced steering stability on wet road surfaces and reduced exterior vehicle noise. BACKGROUND ART

[0002] In pneumatic tires, it has been proposed to increase the groove area of the tread pattern in order to improve steering stability performance and braking performance on wet road surfaces (for example, see Patent Document 1). However, such a method is in a trade-off relationship with the reduction of exterior vehicle noise (pass-by noise), and in recent years, it is required to simultaneously achieve compatibility with the reduction of exterior vehicle noise for which laws and regulations have been tightened. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0003] PATENT DOCUMENT 1 Japanese Unexamined Patent Publication No. 2010-254092 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0004] An object of the present invention is to provide a pneumatic tire that enables improved steering stability on dry road surfaces while achieving both enhanced steering stability on wet road surfaces and reduced exterior vehicle noise. MEANS FOR SOLVING THE PROBLEM

[0005] The pneumatic tire of the present invention, which achieves the above objective, is characterized in that four main grooves extending in the circumferential direction of the tire are formed in the tread portion, these main grooves divide the land portion into five rows, the four main grooves include a pair of center main grooves and a pair of shoulder main grooves located on the outside in the tire width direction, one of the pair of center main grooves is zigzag shaped, at least one of the five rows of land portion has a plurality of lug grooves that extend in the tire width direction with at least one end terminating within the land portion, and of the groove portions on both sides of the lug groove divided at the groove width center position, the groove volume SA of one groove portion is smaller than the groove volume SB of the other groove portion, and the relationship SA / SB ≤ 0.95 is satisfied between the groove volume SA and the groove volume SB.

[0006] Furthermore, the pneumatic tire of the present invention is a pneumatic tire in which the mounting direction to the vehicle is specified, wherein four main grooves extending in the circumferential direction of the tire are formed in the tread portion, these main grooves divide the land portion into five rows, the four main grooves include a pair of center main grooves and a pair of shoulder main grooves located on the outside in the tire width direction, the center main groove located on the outside of the vehicle has a zigzag shape, a plurality of shoulder lug grooves extending in the tire width direction are formed in the shoulder land portion located on the outermost side in the tire width direction, one end of which terminates within the shoulder land portion, and the groove volume SA of one groove portion of the shoulder lug groove divided at the groove width center position is smaller than the groove volume SB of the other groove portion, and the relationship SA / SB ≤ 0.95 is satisfied between the groove volume SA and the groove volume SB. [Effects of the Invention]

[0007] In this invention, one of the pair of center main grooves has a zigzag shape, which provides an edge effect and improves handling stability on wet surfaces. Furthermore, because a lug groove is formed in which at least one end terminates within the land area, passing noise can be reduced, thus achieving both handling stability on wet surfaces and reduced passing noise. In addition, the groove volume SA of one side of the groove portion divided at the center position of the groove width of the lug groove is smaller than the groove volume SB of the other side of the groove portion, and these groove volumes SA and SB satisfy the relationship SA / SB ≤ 0.95, so the groove volume of the lug groove differs on the front side and the rear side of the contact with the ground with respect to the groove width center position (the internal shape of the lug groove is asymmetrical with respect to the groove width center position), resulting in a frequency dispersion effect and contributing to the reduction of passing noise. In particular, in pneumatic tires with a specified mounting direction to the vehicle, the shoulder lug groove does not communicate with the shoulder main groove, and the groove volumes SA and SB in the shoulder lug groove satisfy the above relationship, so that the effect of reducing passing noise can be significantly obtained.

[0008] In the pneumatic tire of the present invention, it is preferable that one groove portion included in the shoulder lug groove on the inside of the vehicle and one groove portion included in the shoulder lug groove on the outside of the vehicle are located on opposite sides in the circumferential direction of the tire. As a result, different frequencies are generated in the shoulder lug grooves on the inside and outside of the vehicle, rather than the same frequencies, thus achieving a frequency dispersion effect and contributing to a further reduction of passing noise.

[0009] Preferably, a chamfered portion is formed on only one of the pair of groove walls that make up the shoulder lug groove, and the chamfered portion in the shoulder lug groove on the inside of the vehicle and the chamfered portion in the shoulder lug groove on the outside of the vehicle are located on opposite sides of each other in the circumferential direction of the tire. This effectively reduces passing noise.

[0010] The ratio Wsh of the shoulder lug groove and Wm of the chamfered portion included in the shoulder lug groove preferably satisfies the relationship 0.17 ≤ Wm / Wsh ≤ 0.60, and more preferably 0.20 ≤ Wm / Wsh ≤ 0.50. By setting the ratio Wm / Wsh appropriately in this way, the amount of noise passing through can be effectively reduced.

[0011] It is preferable that multiple sipes are formed on the land portion adjacent to the main shoulder groove, extending in the tire width direction from both sides of the main shoulder groove in the tire width direction. By providing such sipes, an edge effect can be obtained, thereby improving handling stability on wet surfaces, and tread rigidity can be ensured, thereby simultaneously improving handling stability on dry surfaces. Furthermore, it is also possible to maintain good noise levels when passing over the tire.

[0012] It is preferable that a circumferential auxiliary groove extending in the circumferential direction of the tire is formed in the land area partitioned by the center main groove and the shoulder main groove on the inside of the vehicle. By providing a circumferential auxiliary groove on the inside of the vehicle in this way, the edge component is increased on the opposite side from the center main groove on the outside of the vehicle, which has a zigzag shape, and steering stability on wet road surfaces can be effectively improved.

[0013] Preferably, the shoulder lug grooves on the inner and outer sides of the vehicle are curved to protrude to one side in the circumferential direction of the tire, and a chamfered portion is formed on the groove wall on the protruding side of the shoulder lug groove. By providing such a chamfered portion, an edge effect can be obtained, thereby improving handling stability on wet surfaces, and tread rigidity can be ensured, thereby simultaneously improving handling stability on dry surfaces. [Brief explanation of the drawing]

[0014] [Figure 1] This is a meridian cross-sectional view showing an example of a pneumatic tire according to an embodiment of the present invention. [Figure 2] Figure 1 is an unfolded diagram showing the tread pattern of a pneumatic tire. [Figure 3] (a) and (b) show enlarged views of the lug grooves formed in the tread portion; (a) is a plan view of the lug groove, and (b) is a cross-sectional view of (a) taken along the arrow bb. [Modes for carrying out the invention]

[0015] The configuration of the present invention will now be described in detail with reference to the attached drawings. Figures 1 and 2 show a pneumatic tire according to an embodiment of the present invention. The tire shown in Figures 1 and 2 has a specified mounting direction relative to the vehicle. IN indicates the area inside the tire centerline CL relative to the vehicle when the tire is mounted on the vehicle (hereinafter referred to as the "inside of the vehicle"), and OUT indicates the area outside the tire centerline CL relative to the vehicle when the tire is mounted on the vehicle (hereinafter referred to as the "outside of the vehicle").

[0016] As shown in Figure 1, the pneumatic tire of this embodiment comprises a tread portion 1 that extends in the circumferential direction of the tire and forms 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 radially inner side of these sidewall portions 2. For example, at least the sidewall portion 2 on the outside of the vehicle has a mounting direction indicator portion 2A that indicates the mounting direction relative to the vehicle. On the outside of the vehicle, the mounting direction indicator portion 2A displays, for example, "OUTSIDE" along the circumferential direction of the tire, and on the inside of the vehicle, it displays, for example, "INSIDE" along the circumferential direction of the tire.

[0017] A carcass layer 4 is mounted between a pair of bead sections 3, 3. This carcass layer 4 includes multiple reinforcing cords extending in the radial direction of the tire, which are folded back from the inside to the outside of the tire around the bead core 5 located in each bead section 3. A bead filler 6 made of a rubber composition with a triangular cross-section is placed on the outer circumference of the bead core 5.

[0018] On the other hand, a plurality of belt layers are embedded on the outer peripheral side of the carcass layer in the tread portion. These belt layers each include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged such that the reinforcing cords intersect with each other between layers. In the belt layers, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set, for example, in the range of 10° to 40°. Steel cords are preferably used as the reinforcing cords of the belt layers. On the outer peripheral side of the belt layers, for the purpose of improving high-speed durability, at least one belt cover layer formed by arranging reinforcing cords at an angle of, for example, 5° or less with respect to the tire circumferential direction is disposed. As the reinforcing cords of the belt cover layer, organic fiber cords such as nylon and aramid are preferably used.

[0019] The above-described tire internal structure shows a representative example of a pneumatic tire, but is not limited thereto.

[0020] As shown in Figure 2, four main grooves extending in the tire circumferential direction are formed in the tread portion, and these four main grooves partition five rows of land portions. The main grooves are grooves that perform the main drainage function, and preferably have a groove width set in the range of 6.5 mm to 16.5 mm, and a groove depth set in the range of 6.0 mm to 8.5 mm. The main grooves include an inner shoulder main groove, an inner center main groove, an outer center main groove, and an outer shoulder main groove that are sequentially arranged from the vehicle inner side toward the vehicle outer side, and the five rows of land portions include an inner shoulder land portion, an inner intermediate land portion, a center land portion, an outer intermediate land portion, and an outer shoulder land portion that are sequentially arranged from the vehicle inner side toward the vehicle outer side. The outer center main groove has a zigzag shape.

[0021] In the inner shoulder land portion 21, one first circumferential auxiliary groove 31 extending in the tire circumferential direction is formed, and a plurality of inner shoulder lug grooves 41 extending in the tire width direction and first sipes 51 extending in the tire width direction are formed at intervals in the tire circumferential direction. The inner shoulder lug groove 41 communicates with the first circumferential auxiliary groove 31 and terminates within the inner shoulder land portion 21. In the inner shoulder lug groove 41, a chamfered portion 70 is formed along the extending direction of the inner shoulder lug groove 41 on only one of a pair of groove walls (the groove wall on the front ground contact side and the groove wall on the rear ground contact side). The first sipe 51 has one end communicating with the first circumferential auxiliary groove 31 and the other end communicating with the inner shoulder main groove 11.

[0022] In the inner middle land portion 22, one second circumferential auxiliary groove 32 extending in the tire circumferential direction is formed, and a plurality of second sipes 52 each having one end communicating with the inner shoulder main groove 11 on the vehicle inner side and the other end communicating with the second circumferential auxiliary groove 32, and a plurality of third sipes 53 each having one end communicating with the inner center main groove 12 on the vehicle inner side and the other end communicating with the second circumferential auxiliary groove 32 are formed at intervals in the tire circumferential direction. In the second sipe 52, chamfered portions 80 are formed along the extending direction of the sipe on the groove walls on both the front ground contact side and the rear ground contact side.

[0023] In the center land portion 23, a plurality of fourth sipes 54 each having one end communicating with the inner center main groove 12 on the vehicle inner side and the other end communicating with the outer center main groove 13 on the vehicle outer side are formed at intervals in the tire circumferential direction.

[0024] In the outer middle land portion 24, a plurality of fifth sipes 55 each having one end communicating with the outer shoulder main groove 14 on the vehicle outer side and the other end terminating within the outer middle land portion 24 are formed at intervals in the tire circumferential direction. In the fifth sipe 55, chamfered portions 80 are formed along the extending direction of the sipe on the groove walls on both the front ground contact side and the rear ground contact side. The fifth sipe 55 has a bent portion that is bent in a hook shape toward one side in the tire circumferential direction on the termination side. A plurality of narrow grooves 33 extending intermittently along the tire circumferential direction without communicating with the bent portion are formed at intervals in the tire circumferential direction.

[0025] The outer shoulder land portion 25 has multiple outer shoulder lug grooves 42 extending in the tire width direction, and multiple sixth sipes 56, one end of which communicates with the outer shoulder main groove 14 on the outside of the vehicle and the other end which terminates within the outer shoulder land portion 25, formed at intervals in the tire circumferential direction. The outer shoulder lug grooves 42 terminate within the outer shoulder land portion 25. The outer shoulder lug grooves 42 have a chamfered portion 70 formed along the direction of extension of the outer shoulder lug groove 42 on only one of the groove walls on the front side of the contact point or the groove wall on the rear side of the contact point.

[0026] In the above-described pneumatic tire, as shown in Figures 3(a) and (b), the groove width center position that defines the groove width center of the lug groove 40, which includes the inner shoulder lug groove 41 and the outer shoulder lug groove 42, is defined as P. Of the groove portions on both sides separated by this groove width center position P, the groove volume SA of one groove portion is smaller than the groove volume SB of the other groove portion, and these groove volumes SA and SB are configured to satisfy the relationship SA / SB ≤ 0.95. In particular, it is preferable that the relationship SA / SB ≤ 0.85 is satisfied, and it is more preferable that the relationship SA / SB ≤ 0.70 is satisfied. Furthermore, it is desirable that the relationship 0.20 ≤ SA / SB is satisfied. In the present invention, when comparing the volumes of the groove portions on both sides separated by the groove width center position P of the lug groove 40, if a chamfered portion 70 is provided in the lug groove 40, the groove width center position P is defined based on the groove width of the lug groove 40 including the chamfered portion 70.

[0027] As a method for making the volume of each groove portion different on both sides (front and rear of ground contact) of the center position P of the lug groove 40, examples include providing a chamfered portion 70 on one side of the groove wall of the lug groove 40, or making the groove wall angles θ (see Figure 3(b)) on both sides of the lug groove 40 different from each other. Furthermore, the groove volume of the lug groove 40 may be made different in the inner shoulder lug groove 41 on the inside of the vehicle and the outer shoulder lug groove 42 on the outside of the vehicle using the same method described above, or the groove volume of the lug groove 40 may be made different from each other using different methods.

[0028] In the pneumatic tire described above, the outer center main groove 13 has a zigzag shape, which provides an edge effect and improves handling stability on wet surfaces. Furthermore, the lug groove 40, in which at least one end terminates within the ground portion, is formed, thereby reducing passing noise, thus achieving both handling stability on wet surfaces and reduced passing noise. In addition, of the groove portions on both sides of the lug groove 40, which are divided at the groove width center position P, the groove volume SA of one side is smaller than the groove volume SB of the other side, and these groove volumes SA and SB satisfy the relationship SA / SB ≤ 0.95. As a result, the groove volume of the lug groove 40 differs on the front and rear sides of the contact point with respect to the groove width center position P, which creates a frequency dispersion effect and contributes to the reduction of passing noise. In particular, in pneumatic tires with a specified mounting direction for the vehicle, the inner shoulder lug groove 41 and the outer shoulder lug groove 42 are not in communication with the shoulder main grooves 11 and 14, and the groove volumes SA and SB in the inner shoulder lug groove 41 and the outer shoulder lug groove 42 satisfy the above relationship, thereby significantly reducing passing noise.

[0029] In the above-described pneumatic tire, it is preferable that one groove portion included in the inner shoulder lug groove 41 on the inside of the vehicle and one groove portion included in the outer shoulder lug groove 42 on the outside of the vehicle are located on opposite sides in the circumferential direction of the tire. This means, for example, that the groove volume SA included in the inner shoulder lug groove 41 is located on the front side of the contact with the ground, while the groove volume SA included in the outer shoulder lug groove 42 is located on the rear side of the contact with the ground. With this configuration, different frequencies are generated in the inner shoulder lug groove 41 and the outer shoulder lug groove 42, rather than the same frequencies, thus achieving a frequency dispersion effect and contributing to a further reduction of passing noise.

[0030] The chamfered portion 70 is formed on only one of the pair of groove walls that make up the shoulder lug groove, and it is preferable that the chamfered portion 70 included in the inner shoulder lug groove 41 on the inside of the vehicle and the chamfered portion 70 included in the outer shoulder lug groove 42 on the outside of the vehicle are located on opposite sides in the circumferential direction of the tire. This means, for example, that the chamfered portion 70 included in the inner shoulder lug groove 41 is provided on the groove wall on the front side of the contact with the ground, while the chamfered portion 70 included in the outer shoulder lug groove 42 is provided on the groove wall on the rear side of the contact with the ground. By providing the chamfered portion 70 in the inner shoulder lug groove 41 and the outer shoulder lug groove 42 in this way, passing noise can be effectively reduced.

[0031] The groove width Wsh of the shoulder lug groove (see Figure 3(a)) and the width Wm of the chamfered portion 70 included in the shoulder lug groove (see Figure 3(a)) preferably satisfy the relationship 0.17 ≤ Wm / Wsh ≤ 0.60, and more preferably 0.20 ≤ Wm / Wsh ≤ 0.50. This relationship should be satisfied in both the inner shoulder lug groove 41 on the inside of the vehicle and the outer shoulder lug groove 42 on the outside of the vehicle. The groove width Wsh of the shoulder lug groove should preferably be set in the range of 2.0 mm to 4.0 mm. By setting the ratio Wm / Wsh appropriately in this way, passing noise can be effectively reduced.

[0032] It is preferable that sipes 51, 52, 55, and 56 be formed on both sides of the shoulder main groove in the tire width direction in the land area 20 adjacent to the shoulder main groove (inner shoulder land area 21, inner intermediate land area 22, outer intermediate land area 24, and outer shoulder land area 25). By providing such sipes 51, 52, 55, and 56, an edge effect can be obtained, thereby improving handling stability on wet surfaces, and tread rigidity can be ensured, thereby simultaneously improving handling stability on dry surfaces. Furthermore, it is also possible to maintain good noise levels when passing over the tire.

[0033] It is preferable that a second circumferential auxiliary groove 32 be formed in the inner intermediate land area 22, which is partitioned by the inner center main groove 12 and the inner shoulder main groove 11 on the inside of the vehicle. By providing the second circumferential auxiliary groove 32 on the inside of the vehicle in this way, the edge component is increased on the side opposite to the outer center main groove 13 on the outside of the vehicle, which has a zigzag shape, and steering stability on wet road surfaces can be effectively improved. It is preferable that the groove depth of the second circumferential auxiliary groove 32 be set in the range of 10% to 30% of the groove depth of the main groove 10.

[0034] The inner shoulder lug groove 41 on the inside of the vehicle and the outer shoulder lug groove 42 on the outside of the vehicle are curved so as to protrude to one side in the circumferential direction of the tire, and it is preferable that a chamfered portion 70 is formed on the protruding groove wall of each of the inner shoulder lug groove 41 on the inside of the vehicle and the outer shoulder lug groove 42 on the outside of the vehicle. By providing a chamfered portion 70 on the protruding groove wall of the curved shoulder lug groove in this way, an edge effect can be obtained, thereby improving handling stability on wet roads, and tread rigidity can be ensured, thereby simultaneously improving handling stability on dry roads.

[0035] In the embodiment described above, an example was shown in which the inner shoulder lug groove 41 and outer shoulder lug groove 42 are provided only on the inner shoulder land portion 21 and the outer shoulder land portion 25. However, the invention is not limited to this, and lug grooves 40 may be provided additionally or in place of sipes on the other land portions 20 (inner intermediate land portion 22, center land portion 23, outer intermediate land portion 24). [Examples]

[0036] In a tire with a tire size of 245 / 45R20 and a specified mounting direction for the vehicle, four main grooves are formed in the tread area, extending in the circumferential direction of the tire, and these main grooves divide the land area into five rows, and the four main grooves include a pair of center main grooves and a pair of shoulder main grooves located on the outer side in the tire width direction, and multiple shoulder lug grooves are formed in the shoulder land area on the inner and outer sides of the vehicle, extending in the tire width direction, and the presence or absence of a zigzag-shaped center main groove on the outer side of the vehicle, the presence or absence of shoulder lug grooves, the presence or absence of communication between the shoulder lug grooves and the main grooves, and Conventional examples, comparative examples 1 and 2, and pneumatic tires of examples 1 to 7 were manufactured with the following settings: the ratio SA / SB of the shoulder lug grooves, the position of the groove volume SA of the outer shoulder lug grooves, the position of the groove volume SA of the inner shoulder lug grooves, the position of the chamfered portion of the outer shoulder lug grooves, the position of the chamfered portion of the inner shoulder lug grooves, the ratio Wm / Wsh in the shoulder lug grooves, the presence or absence of sipes extending from both sides of each main shoulder groove, the presence or absence of circumferential auxiliary grooves in the intermediate land area on the inner side of the vehicle, and the arrangement of the chamfered portion on the convex side of the curved shoulder lug grooves.

[0037] In Examples 1 and 2, the groove volumes SA and SB of the shoulder lug groove are made different from each other by not providing a chamfered portion on the groove wall of the shoulder lug groove and by making the groove wall angles on the front side and the rear side of the lug groove different.

[0038] Regarding the "Position of groove volume SA of the outer shoulder lug groove" and the "Position of groove volume SA of the inner shoulder lug groove" in Table 1, "Front" means that the groove volume SA contained in the shoulder lug groove is located on the front side of the contact point, and "Rear" means that the groove volume SA contained in the shoulder lug groove is located on the rear side of the contact point. Regarding the "Position of chamfered portion of the outer shoulder lug groove" and the "Position of chamfered portion of the inner shoulder lug groove," "None" means that no chamfered portion is formed on the groove wall of the shoulder lug groove, "Front" means that a chamfered portion is formed on the groove wall on the front side of the contact point of the shoulder lug groove, and "Rear" means that a chamfered portion is formed on the groove wall on the rear side of the contact point of the shoulder lug groove. Regarding the "Arrangement of chamfered portion on the protruding side of the curved shoulder lug groove," "Present" means that the inner and outer shoulder lug grooves are curved so as to protrude on one side in the circumferential direction of the tire, and a chamfered portion is formed on the groove wall on the protruding side of the shoulder lug groove.

[0039] For these test tires, the handling stability performance on wet surfaces, external noise performance, and handling stability performance on dry surfaces were evaluated using the test methods described below, and the results are shown in Table 1.

[0040] Handling stability on wet surfaces: Each test tire was mounted on a 20 x 8.5J rim wheel, and subjective evaluations were conducted by test drivers on a wet test course under conditions of 250 kPa air pressure. The evaluation results are shown as an index, with the conventional example set to 100. A higher index value indicates better handling stability on wet surfaces.

[0041] External noise performance: Each test tire was mounted on a 20 x 8.5J rim wheel, and tested in accordance with UN. R117 under an air pressure of 250 kPa. The external noise level was measured. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional example set to 100. A higher index value indicates less external noise and superior external noise performance.

[0042] Handling stability on dry surfaces: Each test tire was mounted on a 20 x 8.5J rim wheel, and subjective evaluations were conducted by test drivers on a dry test course under conditions of 250 kPa air pressure. The evaluation results are shown as an index, with the conventional example set at 100. A higher index value indicates better handling stability on dry surfaces.

[0043] [Table 1]

[0044] As can be seen from Table 1, the pneumatic tires of Examples 1 to 7 showed a well-balanced improvement in handling stability on wet surfaces, external noise performance, and handling stability on dry surfaces compared to conventional examples.

[0045] On the other hand, Comparative Example 1 lacked a zigzag-shaped outer center main groove, the shoulder lug groove was connected to the main groove, and the SA / SB ratio was set outside the specified value of the present invention, resulting in poor handling stability and external noise performance on wet surfaces. Comparative Example 2 also had a SA / SB ratio set outside the specified value of the present invention, resulting in poor handling stability on wet surfaces.

[0046] This disclosure encompasses the following inventions[1] to [8]. The invention [1] is a pneumatic tire characterized in that four main grooves are formed in the tread portion, extending in the circumferential direction of the tire, these main grooves divide five rows of land portions, the four main grooves include a pair of center main grooves and a pair of shoulder main grooves located on the outer side in the tire width direction, one of the pair of center main grooves is zigzag in shape, at least one of the five rows of land portions has a plurality of lug grooves formed in the land portion, at least one end of which terminates within the land portion and extends in the tire width direction, the groove volume SA of one groove portion of the lug grooves divided at the groove width center position is smaller than the groove volume SB of the other groove portion, and the relationship SA / SB ≤ 0.95 is satisfied between the groove volume SA and the groove volume SB. The invention [2] is a pneumatic tire in which the mounting direction to a vehicle is specified, wherein four main grooves extending in the circumferential direction of the tire are formed in the tread portion, these main grooves divide the land portion into five rows, the four main grooves include a pair of center main grooves and a pair of shoulder main grooves located on the outer side in the tire width direction, the center main groove located on the outer side of the vehicle is zigzag in shape, a plurality of shoulder lug grooves extending in the tire width direction are formed in the shoulder land portion located on the outermost side in the tire width direction, one end of which terminates within the shoulder land portion, and the groove volume SA of one groove portion of the shoulder lug groove divided at the groove width center position is smaller than the groove volume SB of the other groove portion, and the relationship SA / SB ≤ 0.95 is satisfied between the groove volume SA and the groove volume SB. Invention [3] is a pneumatic tire according to Invention [2], characterized in that the groove portion on one side included in the shoulder lug groove on the inside of the vehicle and the groove portion on one side included in the shoulder lug groove on the outside of the vehicle are located on opposite sides of each other in the circumferential direction of the tire. Invention [4] is a pneumatic tire according to Invention [2] or [3], characterized in that a chamfered portion is formed on only one of the pair of groove walls constituting the shoulder lug groove, and the chamfered portion included in the shoulder lug groove on the inside of the vehicle and the chamfered portion included in the shoulder lug groove on the outside of the vehicle are located on opposite sides of each other in the circumferential direction of the tire. Invention [5] is a pneumatic tire according to Invention [4], characterized in that the groove width Wsh of the shoulder lug groove and the width Wm of the chamfered portion included in the shoulder lug groove satisfy the relationship 0.17 ≤ Wm / Wsh ≤ 0.60. Invention [6] is a pneumatic tire according to any one of Inventions [1] to [5], characterized in that a plurality of sipes extending in the tire width direction from both sides of the shoulder main groove in the tire width direction are formed on the land portion adjacent to the shoulder main groove. Invention [7] is a pneumatic tire according to any one of Inventions [2] to [5], characterized in that a circumferential auxiliary groove extending in the circumferential direction of the tire is formed in the land area partitioned by the center main groove and the shoulder main groove on the inside of the vehicle. Invention [8] is a pneumatic tire according to any one of Inventions [2] to [5], [7], characterized in that the shoulder lug grooves on the inner and outer sides of the vehicle are curved to protrude to one side in the circumferential direction of the tire, and a chamfered portion is formed on the groove wall on the protruding side of the shoulder lug groove. [Explanation of symbols]

[0047] 1. Tread section 2 Sidewall section 3. Bead section 10,11,12,13,14 Main groove 20,21,22,23,24,25 Land 31,32 Circumferential auxiliary groove 40, 41, 42 lug grooves 51, 52, 53, 54, 55, 56 sipes CL tire centerline P Groove width center position

Claims

1. Four main grooves are formed in the tread portion, extending in the circumferential direction of the tire. These main grooves divide the tread into five rows of land areas, and the four main grooves include a pair of center main grooves and a pair of shoulder main grooves located on the outer side in the tire width direction, with one of the pair of center main grooves having a zigzag shape. In at least one of the five rows of land portions, a plurality of lug grooves are formed, each having at least one end terminated within the land portion and extending in the tire width direction. A pneumatic tire characterized in that, of the groove portions on both sides of the lug groove, separated by the center position of the groove width, the groove volume SA of one groove portion is smaller than the groove volume SB of the other groove portion, and the relationship SA / SB ≤ 0.95 is satisfied between the groove volume SA and the groove volume SB.

2. In pneumatic tires with a specified mounting direction for the vehicle, Four main grooves are formed in the tread portion, extending in the circumferential direction of the tire. These main grooves divide the tread into five rows of land areas, and the four main grooves include a pair of center main grooves and a pair of shoulder main grooves located on the outer side in the tire width direction. The center main grooves located on the outer side of the vehicle have a zigzag shape. Multiple shoulder lug grooves are formed on the outermost shoulder land portion in the tire width direction, with one end terminating within the shoulder land portion and extending in the tire width direction. A pneumatic tire characterized in that, of the two groove portions separated by the center position of the groove width of the shoulder lug groove, the groove volume SA of one groove portion is smaller than the groove volume SB of the other groove portion, and the relationship SA / SB ≤ 0.95 is satisfied between the groove volume SA and the groove volume SB.

3. The pneumatic tire according to claim 2, characterized in that the groove portion on one side of the shoulder lug groove on the inside of the vehicle and the groove portion on the other side of the shoulder lug groove on the outside of the vehicle are located on opposite sides of each other in the circumferential direction of the tire.

4. The pneumatic tire according to claim 2 or 3, characterized in that a chamfered portion is formed on only one of the pair of groove walls constituting the shoulder lug groove, and the chamfered portion included in the shoulder lug groove on the inside of the vehicle and the chamfered portion included in the shoulder lug groove on the outside of the vehicle are located on opposite sides of each other in the tire circumferential direction.

5. The pneumatic tire according to claim 4, characterized in that the groove width Wsh of the shoulder lug groove and the width Wm of the chamfered portion included in the shoulder lug groove satisfy the relationship 0.17 ≤ Wm / Wsh ≤ 0.

60.

6. The pneumatic tire according to claim 1 or 2, characterized in that a plurality of sipes extending in the tire width direction from both sides of the shoulder main groove in the tire width direction are formed on the land portion adjacent to the shoulder main groove.

7. The pneumatic tire according to claim 2 or 3, characterized in that a circumferential auxiliary groove extending in the circumferential direction of the tire is formed in the land area partitioned by the center main groove and the shoulder main groove on the inside of the vehicle.

8. The pneumatic tire according to claim 2 or 3, characterized in that the shoulder lug grooves on the inner and outer sides of the vehicle are curved to protrude to one side in the circumferential direction of the tire, and a chamfered portion is formed on the groove wall on the protruding side of the shoulder lug groove.

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