JP6548495B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as a "tire"), and more specifically, an air capable of sufficiently securing wet braking performance without providing lug grooves and capable of improving wear resistance. It relates to a tire containing.

  The pneumatic tire is required to have both wet performance and uneven wear resistance, and the tread pattern has a rib basic pattern (rib lug pattern) based on circumferential grooves (rib grooves) extending in the circumferential direction of the tire. Is common. In a tire having a rib lug pattern, drainage in the longitudinal direction of the tire is performed by circumferential grooves, and drainage to the side of the tire is performed by lateral grooves.

  In such a tire, in Patent Document 1, when the circumferential rigidity per unit length in the circumferential direction of each circumferential land portion is KX in order to improve the handle response performance, the circumferential land portion of the center land portion is It has been proposed to make the circumferential rigidity KXc smaller than the circumferential rigidity KXs of the circumferential land portion of the shoulder.

JP, 2009-35130, A

  On the other hand, in order to make wear of the tread portion uniform, it is effective to reduce the difference between the rigidity of the shoulder land portion and the rigidity of the center land portion. Therefore, in order to increase the rigidity of the center land portion, it is conceivable that no lug groove is provided in the center land portion. However, if the lug grooves are not provided at the center land portion, the drainage performance is reduced, and there is a concern that the wet braking performance may be reduced.

  Therefore, an object of the present invention is to provide a pneumatic tire capable of sufficiently securing wet braking performance without providing a lug groove and capable of improving wear resistance.

  As a result of intensive studies to solve the above problems, the present inventors set the block rigidity of each of the center land portion and the shoulder land to a predetermined value, and form the sipes in the center land portion to achieve the above object. It has been found that the present invention can be accomplished.

That is, the pneumatic tire according to the present invention is a pneumatic tire having a land portion divided by a plurality of circumferential grooves extending continuously in the tire circumferential direction in a tread portion formed in an annular shape,
When the land portion closest to the tire equator is the center land portion, and the outermost land portions in the tire width direction are shoulder land portions, circumferential block rigidity of the center land portion / circumferential block stiffness of the shoulder land portion The ratio is 0.66 to 0.78, and a sipe is provided in the center land portion.

  In the tire according to the present invention, the ratio of the width direction block stiffness of the center land portion to the width direction block stiffness of the shoulder land portion is preferably 0.66 or more. Further, in the tire according to the present invention, a ratio I of circumferential block stiffness of the center land portion / circumferential block stiffness of the shoulder land portion, width direction block stiffness of the center land portion / width direction of the shoulder land portion The ratio (I / II) of the block rigidity ratio II to the ratio II is preferably 1.01 or more. Furthermore, in the tire according to the present invention, it is preferable that notches be provided on the tread surface side in the sipes penetrating through the circumferential grooves on both sides defining the center land portion among the sipes. Furthermore, in the tire according to the present invention, it is preferable that the depth d of the notch is 0.3 to 5 mm, and the width of the opening is 0.6 to 10 mm.

  According to the present invention, it is possible to provide a pneumatic tire capable of sufficiently securing the wet braking performance without providing the lug grooves and capable of improving the wear resistance.

BRIEF DESCRIPTION OF THE DRAWINGS It is an expanded view of the tread part which shows one suitable example of the tread pattern of the pneumatic tire concerning this invention. It is a width direction sectional view near the width direction Sipe provided in the center land part in one embodiment of the pneumatic tire concerning the present invention. FIG. 1 is a widthwise cross-sectional view of a tire according to a preferred embodiment of a pneumatic tire according to the present invention.

Hereinafter, the pneumatic tire of the present invention will be described in detail using the drawings.
FIG. 1 is a development view of a tread portion showing one preferable example of a tread pattern of a pneumatic tire according to the present invention. The tire according to the present invention has land portions 2 divided by a plurality of (three in the illustrated example) circumferential grooves 1 extending continuously in the circumferential direction of the tire in a tread portion 10 formed in an annular shape. . In the tire according to the present invention, when the land portion 2 closest to the tire equator CL is the center land portion 2a, and the outermost land portions 2 in the tire width direction are shoulder land portions 2b, the center land portion 2a has a lug groove. It is not a structure. Thereby, the rigidity of the center land portion 2a can be enhanced, and as a result, the difference in rigidity between the center land portion 2a and the shoulder land portion 2b can be reduced. Thereby, the wear of the center land portion 2a and the shoulder land portion 2b of the tread portion 10 can be made uniform.

  However, when the lug grooves are not provided in the center land portion 2a, there is a possibility that the drainage performance may be reduced. Therefore, in the tire of the present invention, the wet braking performance is secured by providing the sipe 3 in the center land portion 2a to secure the drainage performance. In the illustrated example, the circumferential sipe 3a extending in the circumferential direction and the widthwise sipe 3b extending obliquely in the tire width direction are provided, and the widthwise sipe 3b is provided on both sides defining the center land portion 2a. It penetrates into the main direction groove 1. The pitch of the widthwise sipe 3b is preferably 12 mm to 42 mm from the viewpoint of wet braking performance. The number of circumferential grooves 1 varies depending on the size of the tire etc. However, in the case of a passenger car tire, the number of circumferential grooves 1 may be three as shown in the illustrated example, and the tire equator CL may be sandwiched by two rows of center land portions. it can.

  Further, in the tire of the present invention, the ratio of the circumferential block stiffness of the center land portion 2a to the circumferential block stiffness ratio of the shoulder land portion 2b is set to 0.66 or more. The abrasion resistance can be improved by setting the ratio of the circumferential direction block stiffness of the center land portion 2 a to the circumferential direction block stiffness of the shoulder land portion 2 b to 0.66 or more. The upper limit of the ratio of the circumferential block stiffness of the center land portion 2a to the circumferential block stiffness ratio of the shoulder land portion 2b is not particularly limited, and can be appropriately designed without impairing other performances. If the rigidity of the circumferential block rigidity of 2a becomes high, slippage may occur in wet braking, so the range of the ratio of the circumferential block rigidity of the center land portion 2a / the circumferential block rigidity ratio of the shoulder land portion 2b is Preferably, it is 0.66 to 0.78.

  In the tire according to the present invention, the ratio of the width direction block stiffness of the center land portion 2a to the width direction block stiffness of the shoulder land portion 2b is preferably 0.66 or more. The wear resistance can be further improved by setting the ratio of the width direction block stiffness of the center land portion 2 a to the width direction block stiffness of the shoulder land portion 2 b to be 0.66 or more. In the tire of the present invention, the upper limit of the ratio of the width direction block stiffness of the center land portion 2a to the width direction block stiffness of the shoulder land portion 2b is also not particularly limited, and should be appropriately designed within a range that does not impair other performances. However, if the rigidity of the center land portion 2a in the width direction block rigidity is high, slippage may occur in wet braking as well, so the width direction block stiffness of the center land portion 2a / width direction of the shoulder land portion 2b The range of the block stiffness ratio is preferably 0.66 to 0.78.

  In the tire according to the present invention, the ratio of the circumferential block stiffness of the center land portion 2a / the circumferential block stiffness ratio of the shoulder land portion 2b and the width direction block stiffness of the center land portion 2a / the width direction block of the shoulder land portion 2b The ratio of the rigidity to the ratio is preferably 1.01 or more. By satisfying such conditions, the wet braking performance and the wear resistance can be highly balanced. Preferably it is 1.01-1.12.

  In the tread pattern shown in FIG. 1, the center land portion 2a has a width extending in the tire width direction penetrating the circumferential sipe 3a extending in the circumferential direction and the circumferential grooves 1 on both sides defining the center land portion 2 In the tire of the present invention, the notch portion 4 is provided on the tread tread side of the widthwise sipe 3b among the sipe 3 provided in the center land portion 2a, although it has the direction sipe 3b. Is preferred. FIG. 2 is a width direction cross-sectional view in the vicinity of a width direction sipe provided in a center land portion in an embodiment of the pneumatic tire according to the present invention. In the example of illustration, although the shape of the notch part 4 is a taper shape in the width direction cross section, it is not restricted to this. By providing the notched portion 4 on the tread tread side, drainage performance can be further improved, and thereby, wet braking performance can be further enhanced.

  In the tire according to the present invention, as shown in FIG. 2, when the cross-section in the width direction is tapered as the shape of the notch 4, the depth d of the notch 4 is 0.3 from the viewpoint of drainage. About 5 mm is preferable, and the width w of the opening of the notch 4 is preferably about 0.6 to 10 mm.

  The tire according to the present invention has a center land portion 2a divided by a plurality of circumferential grooves 1 continuously extending in the circumferential direction of the tire, in a tread portion 10 formed annularly, and the periphery of the center land portion 2a The ratio of the direction block stiffness / circumferential block stiffness of the shoulder land portion 2b is set to 0.66 or more, and by providing the sipe 3 on the center land portion 2b, the wet braking performance and the wear resistance are both highly achieved. Other than this, known structures can be adopted.

  For example, as shown in the figure, the center land portion 2a may be provided with a circumferential sipe 3a extending in the circumferential direction in addition to the widthwise sipe 3b, and the sipe 3c or groove may be appropriately provided to the shoulder land portion 2b. 5 may be provided. Further, the width and the depth of the circumferential groove 2a, the circumferential sipe 3a, the widthwise sipe 3b, the sipe 3c provided in the shoulder land portion, and the groove 5 can be configured similar to those of known tires.

  Next, FIG. 3 shows a widthwise sectional view of a tire according to a preferred embodiment of the pneumatic tire according to the present invention. In the illustrated tire 100 of the present invention, bead cores 12 are embedded in a pair of bead portions 11 respectively, and the carcass 13 is folded around the bead cores 12 from the inside to the outside of the tire and locked. Further, a belt 14 comprising two belt layers 14 a and 14 b is provided on the radially outer side of the carcass 13, and a tread portion 10 made of tread rubber is provided on the outer periphery of a crown portion of the belt 14. The sidewall portions 15 are respectively disposed. As a gas with which the tire 100 of the present invention is filled, an inert gas such as nitrogen, argon, or helium can be used in addition to normal air or air whose oxygen partial pressure has been adjusted.

Hereinafter, the present invention will be described in more detail using examples.
Examples 1 to 6 and Comparative Examples 1 and 2
A tire having a tread pattern shown in FIG. 1 was produced at a tire size of 165 / 650R15. (A) ratio of circumferential block stiffness of center land portion 2a to circumferential direction block stiffness ratio of shoulder land portion 2b, (B) width direction block stiffness of center land portion 2a, width direction block stiffness of shoulder land portion 2b Ratio, (C) ratio of circumferential direction block stiffness of center land portion 2a to circumferential direction block stiffness ratio of shoulder land portion 2b, and ratio of width direction block stiffness of center land portion 2a to width direction block stiffness of shoulder land portion 2b About the presence or absence of the notch part 4 provided in (A) / (B) and (D) Sipe 3, it is as showing in Table 1. FIG. The cross-sectional shape of the notch 4 is a tapered shape as shown in FIG. 2, the depth d of the notch 4 is 1.0 mm, and the width of the opening w is 2.0 mm.

<Wet braking performance>
Wet braking performance was evaluated according to the conditions of the Automobile Accident Countermeasures Mechanism (JNCAP). The condition is that the test tire is mounted on a real vehicle (equivalent to two front seats: 65 kg × 2) and braking is performed when the vehicle is fully braked from 100 km / h on a test track with a wet road surface temperature of 27.0 ± 5 ° C. The distance was measured. The results are shown in Table 1.

<Abrasion resistance>
Each of the obtained tires was attached to a 14 × 4.5 J rim, mounted on a vehicle, and run on a test course for 600 km to evaluate the wear resistance of the tire. The results are shown in Table 1. The internal pressure of the tire was 240 kPa, and the load was equivalent to two front seats, 65 kg × 2.

  From Table 1, it can be seen that the tire of the present invention can sufficiently secure wet braking performance without providing the lug grooves, and can improve the wear resistance.

Reference Signs List 1 circumferential groove 2 land portion 2a center land portion 2b shoulder land portion 3 sipe 3a circumferential direction sipe 3b width direction sipe 4 cutaway portion 5 groove 10 tread portion 11 bead portion 12 bead core 13 carcass 14 belt 14a, 14b belt layer 15 side Wall part 100 pneumatic tire (tire)

Claims (5)

A pneumatic tire having land portions defined by a plurality of circumferential grooves continuously extending in the circumferential direction of the tire, in an annularly formed tread portion,
When the land portion closest to the tire equator is the center land portion, and the outermost land portions in the tire width direction are shoulder land portions, circumferential block rigidity of the center land portion / circumferential block stiffness of the shoulder land portion A pneumatic tire having a ratio of 0.66 to 0.78 and a sipe provided on the center land portion.   The pneumatic tire according to claim 1, wherein a ratio of a width direction block stiffness of the center land portion to a width direction block stiffness of the shoulder land portion is 0.66 or more.   The ratio of the ratio of the circumferential block stiffness of the center land portion to the circumferential block stiffness of the shoulder land portion and the ratio of the width direction block stiffness of the center land portion to the width direction block stiffness of the shoulder land portion is 1 The pneumatic tire according to claim 1 or 2, which is .01 or more.   The pneumatic tire according to any one of claims 1 to 3, wherein a notch is provided on the tread tread side in the sipe penetrating the circumferential grooves on both sides of the sipe that divides the center land portion. tire. The pneumatic tire according to claim 4, wherein the depth d of the notched portion is 0.3 to 5 mm, and the width of the opening is 0.6 to 10 mm.

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