JP2015009627A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which can improve on-ice performance and dry performance by making ground pressure uniform by suppressing buckling of a tread surface.SOLUTION: Plural sipings 14 are disposed on a land part 13 formed on a tread surface 10 in a tire circumferential direction with intervals. Among the plural sipings 14, siping width D of the inside siping 15 included in a center side area Ce disposed on a tire width direction inside of the tread surface 10 is larger than siping width d of the outside siping 16 included in a shoulder side area Sh disposed on a tire width direction outside of the tread surface 10.

Description

  The present invention relates to a pneumatic tire having a plurality of sipes on a tread surface, and more specifically, it is possible to improve on-ice performance and dry performance by suppressing the tread surface buckling and making the contact pressure uniform. It relates to a pneumatic tire.

  Winter tires such as studless tires used for running on snowy icy roads are required to have excellent driving stability such as driving performance, braking performance and turning performance during running on snowy icy roads. For this reason, conventionally, a land portion composed of blocks and ribs divided by circumferential grooves and lateral grooves is provided in the tread portion, and a plurality of sipes are formed on the land portion, thereby increasing the flexibility of the land portion and the actual ground contact area. In addition, the steering stability (performance on ice) on ice is ensured by the scratching action (edge effect) by the edges of these sipes (see, for example, Patent Document 1).

  By the way, in general, since the tread portion of the pneumatic tire is gently curved in the tire width direction, the circumferential length of the pneumatic tire is different between the center portion and the shoulder portion, and the circumferential length of the center portion is relatively It is getting bigger. Therefore, when the tire contacts the road surface due to the difference in the circumferential length, a buckling in which the center side portion of the tread portion is lifted may occur. When such buckling occurs, there is a problem that the contact pressure becomes uneven and the above-mentioned performance on ice cannot be obtained sufficiently. In addition, uneven contact pressure not only degrades the performance on ice, but also has a problem of adversely affecting the dry performance.

JP 2011-088539 A

  An object of the present invention is to provide a pneumatic tire that can improve performance on ice and dry performance by suppressing buckling of the tread surface and making the contact pressure uniform.

  In order to achieve the above object, the pneumatic tire of the present invention is a pneumatic tire in which a plurality of sipes having a width of 1.5 mm or less are arranged at intervals in the tire circumferential direction on a land portion formed on a tread surface. Of the plurality of sipes, the sipe width of the inner sipe included in the center side region located on the inner side in the tire width direction of the tread surface is the outer sipe included in the shoulder side region located on the outer side in the tire width direction of the tread surface. It is characterized by being larger than the sipe width.

  In the present invention, since the sipe width of the center side region is large as described above, the land portion of the center side region is more easily deformed in the circumferential direction (direction in which the sipe width is narrowed) than the land portion of the shoulder side region. Therefore, when the center side region having a relatively large circumference contacts the ground, it is possible to greatly contract in the circumferential direction so as to eliminate the difference between the original circumference and the contact length, thereby suppressing buckling. be able to. As a result, the contact pressure can be made uniform, and the on-ice performance and the dry performance can be improved.

  In the present invention, the center side region is preferably a region of 30% to 60% of the tread width centering on the tire equator. Thus, buckling can be effectively suppressed by setting a center side area | region.

  In the present invention, the sipe width of the outer sipe is preferably in the range of 0.3 to 0.6 times the sipe width of the inner sipe. By setting the sipe width in this way, buckling can be effectively suppressed while maintaining an excellent edge effect (performance on ice).

  In the present invention, the inclination angle of the outer sipe with respect to the tire width direction is preferably larger than the inclination angle of the inner sipe with respect to the tire width direction. Thereby, buckling can be effectively suppressed.

1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. 1 is a front view showing a tread surface of a pneumatic tire according to an embodiment of the present invention. It is explanatory drawing which showed typically the mode of a deformation | transformation when a pneumatic tire grounds. It is a front view which shows the tread surface of the pneumatic tire which consists of another embodiment of this invention. It is a front view which shows the tread surface of the pneumatic tire which consists of another embodiment of this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, 3 is a bead portion, and E is a tire equator. A carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the tire inner side to the outer side around the bead core 5 disposed in each bead portion 3. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. On the other hand, a plurality of layers (two layers in FIG. 1) of belt layers 7 and 8 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each of the belt layers 7 and 8 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7 and 8, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set, for example, in a range of 10 ° to 40 °. Further, a belt reinforcing layer 9 is provided on the outer peripheral side of the belt layers 7 and 8. The belt reinforcing layer 9 includes an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 9, the organic fiber cord has an angle with respect to the tire circumferential direction set to, for example, 0 ° to 5 °.

  The present invention is applied to such a general pneumatic tire, but its cross-sectional structure is not limited to the basic structure described above.

  As illustrated in FIG. 2, the outer surface of the tread portion 1 of the pneumatic tire of the present invention, that is, the tread surface 10, has a plurality of (5 in FIG. 2) circumferential grooves 11 extending in the tire circumferential direction. A plurality of (four rows in the tire width direction) land portions 13 are formed by the plurality of lateral grooves 12 extending in the tire width direction.

  In each land portion 13, a plurality of sipes 14 are arranged at intervals in the tire circumferential direction. These sipes 14 have different sipe widths depending on the position in the tire width direction of the land portion 13 where each sipe 14 is formed. Specifically, the sipe 14 is included in the inner sipe 15 included in the center side region Ce positioned on the inner side in the tire width direction of the tread surface 10 and the shoulder side region Sh positioned on the outer side in the tire width direction of the tread surface 10. The sipe width is different between the inner sipe 15 and the outer sipe 16, and the sipe width D of the inner sipe 15 is set larger than the sipe width d of the outer sipe 16. That is, the magnitude relationship between the sipe width D of the inner sipe 15 and the sipe width d of the outer sipe 16 is D> d.

  As schematically shown in FIG. 3, when the pneumatic tire T contacts the road surface R, the contact length L2 on the contact surface is shorter than the original circumferential length L1 of the portion to be contacted. Basically, the pneumatic tire T is deformed so as to eliminate this difference in length (shrinks in the tire circumferential direction) and adheres closely to the road surface R. However, the tread portion 1 of the pneumatic tire T extends in the tire width direction. Since the curve is gently curved and the circumference of the center portion is larger than the circumference of the shoulder portion, the difference between the original circumference L1 and the ground contact length L2 becomes significant at the center portion. Therefore, in the center portion, this difference in length is not sufficiently eliminated, and buckling in which the tread portion 1 of the pneumatic tire T is lifted in the direction of the arrow in the figure is likely to occur.

  On the other hand, in the present invention, the sipe 14 assists contraction in the tire circumferential direction (deformation in the direction of narrowing the width of the sipe 14) to eliminate the above-described difference in length. As described above, since the sipe width D of the inner sipe 15 is set to be relatively large in the center side region Ce, deformation in the direction of narrowing the width of the inner sipe 15 (shrinkage in the tire circumferential direction) is greatly increased. can do. Therefore, buckling that is likely to occur in the center side region Ce can be suppressed, the land portion 13 can be grounded evenly with respect to the road surface regardless of the circumferential length, and the ground pressure can be made uniform. As a result, it is possible to improve on-ice performance and dry performance.

  In the present invention, the sipe 14 is a fine groove having a width of 1.5 mm or less, and the sipe width is an average value of the width of the sipe 14 included in each region. That is, even if the sipe 14 having a different sipe width is included in each region, it is sufficient that the sipe width as a whole has the above-described magnitude relationship. Preferably, sipes 14 having substantially the same width may be disposed in each region, whereby the deformation in the circumferential direction of the land portion 13 in each region can be optimized and buckling can be effectively suppressed. . The sipe 14 included in each region does not necessarily have a constant thickness, and the sipe width may change in one sipe 14. In that case, the maximum width is the width of the sipe.

  In the present invention, the center region Ce is preferably a region of 30% to 60% of the tread width W centered on the tire equator E. In other words, it is preferable to arrange the boundary between the center side region Ce and the shoulder side region Sh at positions of 15% to 30% of the tread width W from the tire equator E to both sides in the tire width direction. The tread width W is a distance between design ends on both sides in the tire width direction.

  By setting in this way, a portion having a relatively large perimeter and where buckling is likely to occur can be set as the center side region Ce where the land portion 13 is easily deformed in the circumferential direction. Can be suppressed. At this time, if the center side region Ce is smaller than 30% of the tread width W, the region in which the sipe having the large sipe width (inner sipe 15) is arranged becomes narrow, so that the effect of suppressing buckling cannot be sufficiently obtained. . If the center-side region Ce is larger than 60% of the tread width W, the ratio of the sipe having a large sipe width (inner sipe 15) in all the sipes 14 becomes too large, and the rigidity of the land portion 13 is lowered. The edge effect is not exhibited. As a result, the effect of improving the performance on ice cannot be obtained sufficiently.

  In the present invention, as illustrated in FIG. 2, it is preferable that the circumferential groove 11 serves as a boundary between the center side region Ce and the shoulder side region Sh, and the sipe width is different for each land portion 13 of each region. For example, as illustrated in FIG. 4, the boundary between the center side region Ce and the shoulder side region Sh may be located on the land portion 13. In this case, the sipe width changes in the land portion 13.

  The sipe width only needs to satisfy the above-described magnitude relationship, but preferably, the sipe width d of the outer sipe 16 is in a range of 0.3 to 0.6 times the sipe width D of the inner sipe 15. That is, the ratio d / D between the sipe width D of the inner sipe 15 and the sipe width d of the outer sipe 16 may be set to 0.3 to 0.6. By setting the ratio of the sipe width in this way, the amount of deformation in the direction of narrowing the width of the sipe 14 in each region can be optimized, the ground pressure can be made more effective, and the excellent edge effect Buckling can be effectively suppressed while maintaining (on-ice performance).

  At this time, if the ratio d / D is smaller than 0.3, the difference in the sipe width becomes too large, the rigidity of the land portion 13 in the center region Ce is excessively lowered, and the edge effect cannot be sufficiently obtained. When the ratio d / D is larger than 0.6, the difference in sipe width is reduced, and the ease of deformation in the circumferential direction of the land portion 13 is hardly changed between the center side region Ce and the shoulder side region Sh. The effect of suppressing this cannot be obtained sufficiently.

  More preferably, the sipe width D of the inner sipe 15 is set to a range of 0.6 mm to 1.4 mm, and the sipe width d of the outer sipe 16 is set to a range of 0.2 mm to 0.8 mm.

  The sipe 14 may all be inclined in the same direction as in the embodiment of FIGS. 2 and 4, but preferably, the inclination angle β of the outer sipe 16 with respect to the tire width direction is set to the inner side as illustrated in FIG. The inclination angle α of the sipe 15 with respect to the tire width direction is set larger than the inclination angle α. That is, the magnitude relationship between the inclination angles α and β of each sipe 14 may be set to α <β. Thus, by making the inclination angle α of the inner sipe 15 relatively small, the land portion 13 of the center side region Ce is easily deformed in the circumferential direction, and buckling can be effectively suppressed.

  More preferably, the inclination angle α of the inner sipe 15 in the center side region Ce is set to 10 ° or less, and the inclination angle β of the outer sipe 16 in the shoulder side region Sh is set to 10 ° to 45 °. If the inclination angle β is 10 ° or less with respect to the inclination angle α of 10 ° or less, the effect of suppressing the difference in the circumferential length / contact length difference between the center region Ce and the shoulder region Sh is reduced. It becomes difficult to sufficiently improve the buckling suppression effect. On the other hand, when the inclination angle β is 45 ° or more, the edge effect by the outer sipe 16 is lowered, so that the effect of improving the braking performance cannot be sufficiently obtained.

  In the present invention, the tread pattern is not limited to the embodiment shown in FIG. 2 and FIGS. For example, the land portion 13 is not limited to the block as in the illustrated example, and may be a rib continuous in the circumferential direction. Further, the circumferential grooves 11 and the lateral grooves 12 are not limited to a linear shape as in the illustrated example, and may have any shape such as a zigzag shape or a curved shape. Furthermore, the tread pattern which does not have the circumferential groove | channel 11 extended in a tire circumferential direction, and formed many V-shaped land parts 13 only by the inclination groove | channel may be sufficient.

  Similarly, the shape of the sipe 14 is not limited to the linear shape shown in FIG. 2 and FIGS. For example, a zigzag shape on the tread surface 10 or a three-dimensional structure that bends in the tread surface 10 and also in the depth direction of the sipe 14 can be used.

  The tire size is 195 / 65R15, has the cross-sectional shape illustrated in FIG. 1, the width of the center region with respect to the tread width, the sipe width of the inner sipe (D), the inclination angle of the inner sipe (α), and the sipe of the outer sipe The conventional example 1, the comparative example 1, and the examples 1 to 13 in which the width (d), the ratio of the inner sipe to the sipe width (d / D), and the inclination angle (β) of the outer sipe are set as shown in Table 1, respectively. Fifteen types of pneumatic tires were produced.

  For these 15 types of pneumatic tires, the braking performance on ice and the dry braking performance were evaluated by the following evaluation methods, and the results are also shown in Table 1.

On-ice braking performance Each test tire is assembled to a wheel with a rim size of 15 x 6 J, mounted on a test vehicle (front-wheel drive vehicle) with an air pressure of 230 kPa and a displacement of 1.4 L, and the ice temperature is in the range of -5 ° C to 0 ° C. In a test course consisting of a certain icy road surface, the braking distance from the running state at a speed of 30 km / h until the vehicle stopped by applying a brake was measured. The evaluation results are shown as index values with the conventional example 1 being 100, using the reciprocal of the measured value. A larger index value means a shorter braking distance and better braking performance on ice.

Dry braking performance Each test tire is mounted on a wheel with a rim size of 15 x 6 J, mounted on a test vehicle (front-wheel drive vehicle) with a displacement of 1.4 liters with an air pressure of 230 kPa, and a speed of 100 km / h on a test course consisting of a dry road surface. The braking distance from when the vehicle was running to when the vehicle was stopped after braking was measured. The evaluation results are shown as index values with the conventional example 1 being 100, using the reciprocal of the measured value. A larger index value means a shorter braking distance and better braking performance on ice.

  As is apparent from Table 1, all of Examples 1 to 13 have improved on-ice braking performance and dry braking performance over Conventional Example 1. In particular, Examples 2 to 3 in which the width of the center region with respect to the tread width is set in a preferable range, and Examples 7 to 3 in which the ratio (d / D) between the sipe width of the outer sipe and the sipe width of the inner sipe is set in a preferable range 8 and 10 to 11 and Examples 12 to 13 in which the inclination angle of the inner sipe was smaller than the inclination angle of the outer sipe, the braking performance on ice and the dry braking performance were remarkably improved.

  On the other hand, in Comparative Example 1 in which the magnitude relationship between the sipe width of the inner sipe and the sipe width of the outer sipe was reversed, the braking performance on ice and the dry braking performance were deteriorated.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7,8 Belt layer 9 Belt reinforcement layer 10 Tread surface 11 Circumferential groove 12 Horizontal groove 13 Land part 14 Sipe 15 Inner sipe 16 Outer sipe E Tire equator Ce Center area Sh Shoulder area W Tread width

Claims (4)

In a pneumatic tire in which a plurality of sipes having a width of 1.5 mm or less are arranged at intervals in the tire circumferential direction on a land portion formed on a tread surface,
Of the plurality of sipes, the sipe width of the inner sipe included in the center side region located on the inner side in the tire width direction of the tread surface is the outer sipe included in the shoulder side region located on the outer side in the tire width direction of the tread surface. A pneumatic tire characterized by being larger than the sipe width.   2. The pneumatic tire according to claim 1, wherein the center side region is a region of 30% to 60% of a tread width centering on the tire equator.   The pneumatic tire according to claim 1 or 2, wherein a sipe width of the outer sipe is in a range of 0.3 to 0.6 times a sipe width of the inner sipe.   The pneumatic tire according to claim 1, wherein an inclination angle of the outer sipe with respect to a tire width direction is larger than an inclination angle of the inner sipe with respect to a tire width direction.

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