JP2019214317A - tire - Google Patents

Abstract

To provide a tire that can make both cornering performance and wet performance on a dry road surface compatible.SOLUTION: The tire has a tread part in which a direction of mounting on a vehicle is specified. The tread part 2 has: an inner tread grounding end Ti; an outer tread grounding end To; an inner main groove 6 continuously extending in a tire circumferential direction between the inner tread grounding end Ti and a tire equator C; an outer narrow groove 7 continuously extending in the tire circumferential direction between the outer tread grounding end To and the tire equator C and having a groove width smaller than that of the inner main groove 6; a center main groove 8 continuously extending in the tire circumferential direction between the inner main groove 6 and the outer narrow groove 7; and an outer crown land part 11 sectioned between the center main groove 8 and the outer narrow groove 7. In the outer crown land part 11 are provided a plurality of outer crown lateral grooves 15 whose both ends terminate in the outer crown land part 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tire, and more particularly, to a tire suitable for high-speed running.

  Patent Literature 1 below proposes a tire used for both running on a public road and running on a circuit. The tire has a first main groove and a second main groove continuously extending in a tire circumferential direction on an inner tread portion between a tire equator and an inner tread ground contact end, in order to ensure wet performance on public road running. Have. Further, in the tire, a groove extending continuously in the tire circumferential direction is not provided in an outer tread portion between the tire equator and the outer tread contact edge.

JP 2017-030604 A

  However, the first main groove and the second lateral groove have a problem that the water between the outer tread portion and the road surface cannot be sufficiently drained during wet running. On the other hand, when the main grooves similar to the first main groove and the second main groove are arranged in the outer tread portion, there is a problem that the pattern rigidity of the outer tread portion decreases, and the cornering performance on a dry road surface deteriorates. .

  The present invention has been devised in view of the above problems, and has as its main object to provide a tire capable of achieving both cornering performance and wet performance on a dry road surface.

  The present invention is a tire having a tread portion in which a mounting direction to a vehicle is designated, wherein the tread portion includes an inner tread grounding end that is inside the vehicle when the vehicle is mounted, and an outer tread that is outside the vehicle when the vehicle is mounted. A ground contact end, an inner main groove continuously extending in the tire circumferential direction between the inner tread ground end and the tire equator, and a tire circumferential direction continuously extending between the outer tread ground end and the tire equator; An outer narrow groove having a smaller groove width than the inner main groove, a central main groove extending continuously in the tire circumferential direction between the inner main groove and the outer narrow groove, the central main groove and the outer narrow groove; It is preferable that the outer crown land portion has a plurality of outer crown lateral grooves whose both ends are interrupted in the outer crown land portion.

  In the tire of the present invention, the tread portion has an outer shoulder land portion partitioned between the outer tread ground end and the outer narrow groove, and the outer shoulder land portion communicates with the outer narrow groove. It is desirable that no lateral groove be provided.

  In the tire of the present invention, it is preferable that the outer shoulder land portion is a plain rib having no groove.

  In the tire according to the aspect of the invention, it is preferable that a groove width of the central main groove is larger than a groove width of the outer narrow groove and smaller than a groove width of the inner main groove.

  In the tire of the present invention, the tread portion has an inner crown land portion partitioned between the inner main groove and the central main groove, and the inner crown land portion extends from the inner main groove and It is preferable that a plurality of inner crown lateral grooves interrupted in the inner crown land portion are provided.

  In the tire of the present invention, it is desirable that the inner crown lateral groove does not intersect with a region where the outer crown lateral groove is projected along the tire axial direction.

  In the tire of the present invention, the tread portion has an inner shoulder land portion partitioned between the inner tread grounding end and the inner main groove, and the inner shoulder land portion has a width from the inner tread grounding end. Preferably, there are provided a plurality of inner shoulder transverse grooves which extend and are interrupted in the inner shoulder land.

  In the tire of the present invention, it is preferable that the inner shoulder lateral groove does not intersect with a region where the outer crown lateral groove is projected along the tire axial direction.

  In the tread portion of the tire of the present invention, an inner main groove extending continuously in the tire circumferential direction between the inner tread contact edge and the tire equator, and a tire circumferential direction continuous between the outer tread contact edge and the tire equator. Outer groove having a groove width smaller than the inner main groove, a central main groove extending continuously in the tire circumferential direction between the inner main groove and the outer narrow groove, a central main groove and an outer narrow groove. An outer crown land portion partitioned between the groove and the groove. Further, the outer crown land portion is provided with a plurality of outer crown lateral grooves whose both ends are interrupted in the outer crown land portion.

  The inner main groove and the central main groove of the present invention are useful, for example, for securing wet performance during straight running and gentle turning. Further, the outer narrow groove having a groove width smaller than the inner main groove, and a plurality of outer crown lateral grooves whose both ends are interrupted in the outer crown land portion are formed in a region between the central main groove of the tread portion and the outer tread grounding end. Drainage can be exhibited while maintaining rigidity. Therefore, the tire of the present invention can achieve both cornering performance on a dry road surface and wet performance.

It is a development view of a tread part of a tire of one embodiment of the present invention. It is the sectional view on the AA line of FIG. It is an enlarged view of the outer crown land part and the outer shoulder land part of FIG. It is an enlarged view of the inner crown land part and the inner shoulder land part of FIG. FIG. 5 is a sectional view taken along line BB of FIG. 4. It is a development view of a tread part of a tire of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a tire 1 of the present embodiment. FIG. 2 is a cross-sectional view taken along line AA of the tread portion 2 of FIG. As shown in FIGS. 1 and 2, the tire 1 of the present embodiment is used, for example, as a pneumatic tire for a passenger car, and particularly as a high-performance tire premised on use on both public roads and circuit running. It is preferably used.

  The tire 1 has a tread portion 2 in which a mounting direction to a vehicle is specified. The direction of attachment to the vehicle is indicated by, for example, characters or marks on a sidewall portion (not shown) or the like. 1 and 2, when the tire 1 is mounted on a vehicle, the left side corresponds to the inside of the vehicle, and the right side corresponds to the outside of the vehicle.

  By designating the direction of attachment to the vehicle, the tread portion 2 has an outer tread contact end To that is outside the vehicle when the vehicle is attached, and an inside tread contact end Ti that is inside the vehicle when the vehicle is attached. .

  The outer tread ground end To and the inner tread ground end Ti are rim-assembled on a regular rim (not shown), are filled with a regular internal pressure, and are loaded with a regular load on the tire 1 in a normal state where no camber is applied. This is the outermost ground contact position in the tire axial direction when grounded on a plane at an angle of 0 °.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, “standard rim” for JATMA, “Design Rim” for TRA, For ETRTO, it is "Measuring Rim".

  "Normal internal pressure" is the air pressure specified for each tire in the standard system including the standard on which the tire is based. For JATMA, the "maximum air pressure"; for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in “VARIOUS COLD INFLATION PRESSURES” is “INFLATION PRESSURE” for ETRTO.

  "Regular load" is the load specified for each tire in the standard system including the standard on which the tire is based. For JATMA, "Maximum load capacity"; for TRA, "TIRE LOAD LIMITS" The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES". For ETRTO, it is "LOAD CAPACITY".

  The tread portion 2 includes an outer tread portion 4 between the tire equator C and the outer tread contact end To, and an inner tread portion 5 between the tire equator C and the inner tread contact end Ti. The tread portion 2 has an inner main groove 6, an outer narrow groove 7, and a central main groove 8.

  The inner main groove 6 continuously extends in the tire circumferential direction between the inner tread contact edge Ti and the tire equator C. The outer narrow groove 7 extends continuously in the tire circumferential direction between the outer tread contact edge To and the tire equator C. The outer narrow groove 7 has a smaller groove width than the inner main groove 6. The central main groove 8 extends continuously between the inner main groove 6 and the outer narrow groove 7 in the tire circumferential direction.

  In the present embodiment, the distance L1 in the tire axial direction from the tire equator C to the groove center line of the inner main groove 6 is preferably, for example, 0.50 to 0.65 times the tread half width TWh. The tread half width TWh corresponds to a distance in the tire axial direction from the tire equator C to the outer tread contact end To or from the tire equator C to the inner tread contact end Ti in the normal state.

  The distance L2 in the tire axial direction from the tire equator C to the groove center line of the outer narrow groove 7 is preferably, for example, 0.65 to 0.75 times the tread half width TWh. In a more desirable mode, the outer narrow groove 7 is disposed closer to the outer tread ground end To than the center position of the outer tread portion 4 in the tire axial direction.

  The distance L3 in the tire axial direction from the tire equator C to the groove center line of the central main groove 8 is desirably, for example, 0.15 times or less of the tread half width TWh. In the present embodiment, the central main groove 8 is on the tire equator C, and the groove center line of the central main groove 8 is arranged on the inner tread ground end Ti side of the tire equator C.

  The groove width W1 of the inner main groove 6 and the groove width W3 of the central main groove 8 have a groove width of at least 5.0 mm or more. In the present specification, the “main groove” means a groove having a groove width of 5.0 mm or more and extending continuously in the tire circumferential direction. The groove width corresponds to a distance between two groove edges in a direction orthogonal to the length direction of the groove. In a desirable mode, the groove width W1 of the inner main groove 6 and the groove width W3 of the central main groove 8 are, for example, 7.0% to 20.0% of the tread half width TWh, and more preferably 15.0% to 20%. 0.0%.

  Generally, the tire 1 is often attached to a vehicle with a negative camber. For this reason, the tire 1 tends to exert a relatively large contact pressure on the inner tread portion 5 when traveling straight or when making gentle turns. Therefore, the inner main groove 6 and the central main groove 8 of the present invention are useful for, for example, assuring wet performance during straight running or gentle turning.

  In a more desirable mode, the groove width W3 of the central main groove 8 is larger than the groove width W2 of the outer narrow groove 7 and smaller than the groove width W1 of the inner main groove 6. Such a central main groove 8 can enhance wet performance while maintaining rigidity near the tire equator C.

  The groove width W2 of the outer narrow groove 7 has, for example, a groove width of less than 5.0 mm. The groove width W2 of the outer narrow groove 7 is desirably, for example, 2.5% to 5.5% of the tread half width TWh.

  As shown in FIG. 2, the depth d1 of the inner main groove 6 and the depth d3 of the central main groove 8 are desirably at least 4.0 mm or more. More specifically, it is desirable that the depth d1 of the inner main groove 6 and the depth d3 of the central main groove 8 be 5.0 to 6.5 mm. As a result, the cornering performance on a dry road surface and the wet performance can be enhanced in a well-balanced manner.

  The inner main groove 6 and the central main groove 8 preferably include, for example, a chamfered portion 10 in which a corner between the groove edge 9e and the groove wall 9w is concave. The angle θ1 of the chamfered portion 10 with respect to the tread normal passing through the groove edge 9e is, for example, 35 to 70 °, and more preferably 60 to 70 °. Such a chamfered portion 10 helps to prevent uneven wear of the groove edge while improving drainage of the main groove.

  It is desirable that the depth d2 of the outer narrow groove 7 is at least 2.0 mm or more. The depth d2 of the outer narrow groove 7 of the present embodiment is, for example, 4.5 to 6.0 mm. In a more desirable mode, the depth d2 of the outer narrow groove 7 is smaller than the depth d1 of the inner main groove 6 and the depth d3 of the central main groove 8. Such an outer narrow groove 7 helps to enhance the wet performance while maintaining the rigidity of the outer tread portion 4.

  As shown in FIG. 1, the tread portion 2 has an outer crown land portion 11, an outer shoulder land portion 12, and an inner crown A land portion 13 and an inner shoulder land portion 14 are provided.

  FIG. 3 is an enlarged view of the outer crown land portion 11 and the outer shoulder land portion 12. As shown in FIG. 3, the outer crown land portion 11 is partitioned between the central main groove 8 and the outer narrow groove 7.

  The width W4 of the outer crown land portion 11 in the tire axial direction is preferably, for example, 0.50 to 0.70 times the half tread width TWh.

  The outer crown land portion 11 is provided with a plurality of outer crown lateral grooves 15 whose both ends are interrupted in the outer crown land portion 11. The outer narrow groove 7 having a groove width smaller than the inner main groove 6 and the plurality of outer crown lateral grooves 15 whose both ends are interrupted in the outer crown land portion 11 are formed by the central main groove 8 of the tread portion 2 and the outer tread ground end To. The drainage property can be exhibited while maintaining the rigidity of the region between the two. Therefore, the tire 1 of the present invention can achieve both cornering performance and wet performance on a dry road surface.

  The outer crown lateral groove 15 is desirably disposed at the center of the outer crown land portion 11 in the tire axial direction. Specifically, the outer crown lateral groove 15 desirably crosses the center position of the outer crown land portion 11 in the tire axial direction. Such outer crown lateral grooves 15 can suppress uneven wear of the outer crown lateral grooves 15 while effectively improving cornering performance and wet performance on a dry road surface.

  The distance L4 in the tire axial direction from the end of the outer crown lateral groove 15 on the center main groove 8 side to the groove edge of the center main groove 8 is 0.20 to 0.35 times the width W4 of the outer crown land portion 11. Is desirable. Similarly, the distance L5 in the tire axial direction from the end of the outer crown lateral groove 15 on the outer tread contact end To side to the groove edge of the outer narrow groove 7 is 0.20 to 0.35 of the width W4 of the outer crown land portion 11. Preferably, it is twice.

  In a more desirable mode, it is desirable that each of the distance L4 and the distance L5 is smaller than the length L6 of the outer crown lateral groove 15 in the tire axial direction. The length L6 of the outer crown lateral groove 15 is, for example, 0.40 to 0.50 times the width W4 of the outer crown land portion 11. Thereby, the length of the outer crown lateral groove 15 is ensured, and excellent wet performance is exhibited.

  It is desirable that the outer crown lateral grooves 15 are arranged at an angle of, for example, 45 ° or less with respect to the tire axial direction. The angle of the outer crown lateral groove 15 with respect to the tire axial direction is preferably, for example, 0 to 20 °. Such an outer crown lateral groove 15 can maintain the lateral rigidity of the outer crown land portion 11 and can suppress a decrease in cornering performance on a dry road surface.

  The groove width W5 of the outer crown lateral groove 15 is desirably smaller than the groove width W1 of the inner main groove 6 and the groove width W3 of the central main groove 8, for example. It is desirable that the groove width W5 of the outer crown lateral groove 15 is larger than the groove width W2 of the outer narrow groove 7, for example. Specifically, the groove width W5 of the outer crown lateral groove 15 is desirably, for example, 5.0 to 15.0 mm. Such an outer crown lateral groove 15 can improve cornering performance and wet performance on a dry road surface in a well-balanced manner.

  It is desirable that the depth of the outer crown lateral groove 15 be smaller than the depth d1 (shown in FIG. 2) of the inner main groove 6, for example. Specifically, the depth of the outer crown lateral groove 15 is desirably 0.85 to 0.95 times the depth d1 of the inner main groove 6.

  The pitch P1 in the tire circumferential direction between two outer crown lateral grooves 15 adjacent to each other in the tire circumferential direction is preferably larger than the width W4 of the outer crown land portion 11, for example. Specifically, the pitch P1 of the outer crown lateral grooves 15 is 1.05 to 1.15 times the width W4 of the outer crown land portion 11. Such an arrangement of the outer crown lateral groove 15 helps maintain the rigidity of the outer crown land portion 11. Note that the pitch P1 is defined by the distance between the groove center lines of the two outer crown lateral grooves 15 in the tire circumferential direction.

  The outer shoulder land portion 12 is divided between the outer narrow groove 7 and the outer tread ground end To. The width W6 of the outer shoulder land portion 12 in the tire axial direction is preferably smaller than, for example, the width W4 of the outer crown land portion 11 in the tire axial direction. Specifically, it is desirable that the width W6 of the outer shoulder land portion 12 in the tire axial direction be 0.20 to 0.35 times the tread half width TWh.

  It is preferable that the outer shoulder land portion 12 is not provided with a lateral groove communicating with the outer narrow groove 7. In another embodiment of the present invention, the outer shoulder land portion 12 may be provided with, for example, a lateral groove not communicating with the outer narrow groove 7. The lateral groove is a notch having a width of 1.5 mm or more and extending in the tire axial direction. For this reason, in another embodiment of the present invention, the outer shoulder land portion 12 may be provided with a so-called sipe having a width of, for example, less than 1.5 mm.

  As a more desirable mode, the outer shoulder land portion 12 of the present embodiment is a plain rib provided with no groove and no sipe. Such an outer shoulder land portion 12 can exhibit high lateral rigidity integrally with the outer crown land portion 11, for example, during a sharp turn on a dry road surface.

  FIG. 4 shows an enlarged view of the inner crown land portion 13 and the inner shoulder land portion 14. As shown in FIG. 4, the inner crown land portion 13 is partitioned between the inner main groove 6 and the central main groove 8. The width W7 of the inner crown land portion 13 in the tire axial direction is preferably smaller than, for example, the width W4 of the outer crown land portion 11 in the tire axial direction (shown in FIG. 3). Specifically, the width W7 of the inner crown land portion 13 is preferably, for example, 0.35 to 0.50 times the tread half width TWh.

  The inner crown land portion 13 is provided with, for example, a plurality of inner crown lateral grooves 20. The inner crown lateral groove 20 extends from the inner main groove 6 and is interrupted in the inner crown land portion 13. Such an inner crown lateral groove 20 can provide drainage while maintaining the rigidity of the inner crown land portion 13 on the inner tread ground contact end Ti side.

  The length L7 of the inner crown lateral groove 20 in the tire axial direction is preferably, for example, 0.40 to 0.60 times the width W7 of the inner crown land portion 13 in the tire axial direction.

  The inner crown lateral groove 20 is desirably arranged at an angle of, for example, 45 ° or less with respect to the tire axial direction. The angle of the inner crown lateral groove 20 with respect to the tire axial direction is preferably, for example, 0 to 20 °. Such inner crown lateral grooves 20 help maintain the lateral rigidity of the inner crown land portion 13.

  The groove width W8 of the inner crown lateral groove 20 is desirably smaller than the groove width W1 of the inner main groove 6 and the groove width W3 (shown in FIG. 1) of the central main groove 8, for example. It is desirable that the groove width W8 of the inner crown lateral groove 20 is larger than the groove width W5 (shown in FIG. 3) of the outer crown lateral groove 15, for example. Specifically, the groove width W8 of the inner crown lateral groove 20 is desirably, for example, 5.0 to 15.0 mm.

  It is desirable that the depth of the inner crown lateral groove 20 be larger than, for example, the depth of the outer crown lateral groove 15. The inner crown lateral groove 20 of the present embodiment has the same depth as the inner main groove 6. Such an inner crown lateral groove 20 is useful for suppressing uneven wear of the inner crown land portion 13 while exhibiting excellent wet performance.

  The pitch P2 in the tire circumferential direction between two inner crown lateral grooves 20 adjacent to each other in the tire circumferential direction is, for example, 0.90 to 1.10 times the pitch P1 (shown in FIG. 2) of the outer crown lateral grooves 15. desirable. In the present embodiment, the pitch P2 of the inner crown lateral grooves 20 is the same as the pitch P1 of the outer crown lateral grooves 15.

  As shown in FIG. 1, in a more desirable mode, the inner crown lateral groove 20 desirably does not intersect with a region where the outer crown lateral groove 15 is projected along the tire axial direction. Such an arrangement of the inner crown lateral grooves 20 suppresses a local decrease in rigidity of the tread portion 2. Therefore, at the time of cornering on a dry road surface, the tread portion 2 is deformed such that the entire tread surface follows the road surface, and as a result, excellent treadability and steering stability can be exhibited.

  As shown in FIG. 4, the inner shoulder land portion 14 is divided between the inner tread ground end Ti and the inner main groove 6. The width W9 of the inner shoulder land portion 14 in the tire axial direction is preferably smaller than, for example, the width W7 of the inner crown land portion 13 in the tire axial direction. Specifically, the width W9 of the inner shoulder land portion 14 is desirably 0.20 to 0.35 times the half tread width TWh.

  The inner shoulder land portion 14 is provided with a plurality of inner shoulder lateral grooves 25, for example. The inner shoulder lateral groove 25 extends from the inner tread contact edge and is interrupted in the inner shoulder land portion 14. The inner shoulder lateral groove 25 is disposed so as to cross the inner tread contact end Ti, and the outer end of the inner shoulder lateral groove 25 is located closer to the sidewall portion than the inner tread contact end Ti. Such inner shoulder lateral grooves 25 can enhance the wet performance while maintaining the rigidity of the inner shoulder land portion 14.

  The length L8 in the axial direction of the tire in the tread contact surface of the inner shoulder lateral groove 25 (the length from the inner tread contact end Ti to the inner end of the inner shoulder lateral groove 25) is, for example, the tire of the inner shoulder land portion 14. It is desirable that it is 0.45 to 0.65 times the width W9 in the axial direction. It is more desirable that the inner shoulder lateral groove 25 is, for example, interrupted on the inner main groove 6 side from the center position of the inner shoulder land portion 14 in the tire axial direction.

  It is desirable that the inner shoulder lateral groove 25 is disposed at an angle of, for example, 45 ° or less with respect to the tire axial direction. The angle of the inner shoulder lateral groove 25 with respect to the tire axial direction is preferably, for example, 0 to 20 °. Such an inner shoulder lateral groove 25 can maintain the lateral rigidity of the inner shoulder land portion 14, and can thereby enhance cornering performance on a dry road surface.

  Preferably, the groove width W10 of the inner shoulder lateral groove 25 is smaller than the groove width W1 of the inner main groove 6, for example. The groove width W10 of the inner shoulder lateral groove 25 is preferably larger than the groove width W8 of the inner crown lateral groove 20, for example. Specifically, the groove width W10 of the inner shoulder lateral groove 25 is desirably, for example, 5.0 to 15.0 mm. Such inner shoulder lateral grooves 25 can enhance wet performance while maintaining steering stability on dry road surfaces.

  FIG. 5 is a cross-sectional view of the inner shoulder lateral groove 25 taken along the line BB. As shown in FIG. 5, the depth d4 of the inner shoulder lateral groove 25 is desirably smaller than the depth d1 (shown in FIG. 2) of the inner main groove 6, for example.

  The inner shoulder lateral groove 25 preferably includes, for example, a chamfered portion 27 in which a corner between the groove edge 26e and the groove wall 26w is concave. The angle θ2 of the chamfered portion 27 with respect to the tread normal passing through the groove edge 26e is, for example, 35 to 70 °, and more preferably 60 to 70 °. Such a chamfered portion 27 is useful for suppressing the uneven wear of the edge of the inner shoulder lateral groove 25 while improving drainage of the groove.

  As shown in FIG. 4, the pitch P3 in the tire circumferential direction between two inner shoulder lateral grooves 25 adjacent to each other in the tire circumferential direction is, for example, 0.90 to the pitch P2 (shown in FIG. 2) of the inner crown lateral grooves 20. Preferably, it is 1.10 times. In the present embodiment, the pitch P3 of the inner shoulder lateral groove 25 is the same as the pitch P2 of the inner crown lateral groove 20.

  As shown in FIG. 1, it is desirable that the inner shoulder lateral groove 25 does not intersect, for example, a region where the outer crown lateral groove 15 is projected along the tire axial direction. Such an arrangement of the inner shoulder lateral grooves 25 can suppress a local decrease in rigidity of the tread portion 2 and enhance steering cornering performance on a dry road surface.

  In a more desirable mode, the groove center line of the inner shoulder lateral groove 25 is provided at a position different from the groove center line of the inner crown lateral groove 20 in the tire circumferential direction. However, a part of the inner shoulder lateral groove 25 may intersect with a region where the inner crown lateral groove 20 is projected along the tire axial direction. Such an inner shoulder lateral groove 25 can enhance wet performance while suppressing an excessive decrease in rigidity of the inner tread portion 5.

  As mentioned above, although the tire of one embodiment of the present invention was explained in detail, the present invention is not limited to the above-mentioned specific embodiment, but can be carried out in various modes.

A tire of size 205 / 55R16 having the basic tread pattern of FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, a tire shown in FIG. 6 was prototyped. The tire of the comparative example has, on the outer tread portion a, a main groove d having the same groove width as the inner main groove c arranged on the inner tread portion b. Further, the outer tread portion a has no groove other than the main groove d. The pattern of the comparative example has the same configuration as the pattern of FIG. 1 in a region between the central main groove e and the inner tread ground end Ti. The wet performance and cornering performance on dry road surfaces of each test tire were tested. The common specifications and test methods for each test tire are as follows.
Rim: 16 × 6.5J
Tire pressure: 230kPa

<Wet performance>
Using an inside drum tester, the rate of occurrence of the hydroplaning phenomenon when each test tire traveled on a drum surface having a water depth of 5.0 mm under the following conditions was measured. The result is an index with Comparative Example 1 being 100. The larger the numerical value, the higher the generation speed and the better the wet performance.
Slip angle: 1.0 °
Vertical load: 4.2kN

<Cornering performance on dry road surface>
The cornering performance when traveling on a dry course on the following test vehicle equipped with the above test tires was evaluated based on the driver's sensuality. The results are scored with the comparative example taken as 100, and the larger the numerical value, the better the steering stability.
Test vehicle: 2000 cc displacement, rear wheel drive vehicle Test tire mounting position: All wheels The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples had both cornering performance on a dry road surface and wet performance.

2 Tread 6 Inner main groove 7 Outer narrow groove 8 Central main groove 11 Outer crown land 15 Outer crown lateral groove Ti Inner tread ground end To Outer tread ground end C Tire equator

Claims (8)

A tire having a tread portion whose mounting direction to a vehicle is designated,
The tread portion,
An inner tread grounding end that is inside the vehicle when the vehicle is mounted,
An outer tread grounding end that is on the outside of the vehicle when the vehicle is mounted,
An inner main groove extending continuously in the tire circumferential direction between the inner tread contact edge and the tire equator,
An outer narrow groove extending continuously in the tire circumferential direction between the outer tread contact edge and the tire equator and having a groove width smaller than the inner main groove;
A central main groove extending continuously in the tire circumferential direction between the inner main groove and the outer narrow groove,
An outer crown land portion partitioned between the central main groove and the outer narrow groove,
The outer crown land portion is provided with a plurality of outer crown lateral grooves whose both ends are interrupted in the outer crown land portion,
tire. The tread portion has an outer shoulder land portion partitioned between the outer tread ground end and the outer narrow groove,
The tire according to claim 1, wherein a lateral groove communicating with the outer narrow groove is not provided in the outer shoulder land portion.   The tire according to claim 2, wherein the outer shoulder land portion is a plain rib having no groove.   The tire according to any one of claims 1 to 3, wherein a groove width of the central main groove is larger than a groove width of the outer narrow groove and smaller than a groove width of the inner main groove. The tread portion has an inner crown land portion partitioned between the inner main groove and the central main groove,
The tire according to any one of claims 1 to 4, wherein the inner crown land portion is provided with a plurality of inner crown lateral grooves extending from the inner main groove and being interrupted in the inner crown land portion.   The tire according to claim 5, wherein the inner crown lateral groove does not intersect with a region where the outer crown lateral groove is projected along the tire axial direction. The tread portion has an inner shoulder land portion partitioned between the inner tread ground end and the inner main groove,
The tire according to any one of claims 1 to 6, wherein the inner shoulder land portion is provided with a plurality of inner shoulder lateral grooves extending from the inner tread ground end and interrupting inside the inner shoulder land portion.   The tire according to claim 7, wherein the inner shoulder lateral groove does not intersect with a region where the outer crown lateral groove is projected along the tire axial direction.

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