JP2013035501A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire excellent in the rain groove wander performance while controlling deterioration in the steering stability.SOLUTION: In the pneumatic tire that has a plurality of land parts partitioned by a plurality of circumferential direction straight grooves at a tread, a plurality of minute grooves cut in the tire width direction along at least one of the edge parts of the circumferential direction straight groove are formed, and at the same time a plurality of kinds of the pitches different in the cutout width W of the minute groove are disposed, and the minute groove satisfies the following (a), (b), and (c). (a) The greatest cutout width Wis W<3.0 mm, (b) (the greatest cutout width W)-(the least cutout width W)≥0.5 mm, (c) both the greatest cutout area and the least cutout area exist to the length of ground contact.

Description

  The present invention relates to a pneumatic tire. More specifically, the present invention relates to a pneumatic tire excellent in rain groove wonder performance (hereinafter referred to as RGW performance) while suppressing a decrease in steering stability performance.

  On highways in North America, Europe, Japan (Kyushu, etc.), in order to improve the drainage of the road surface, it is drilled at a predetermined pitch, a predetermined groove depth, and a predetermined groove width in parallel with the direction in which the vehicle travels. A plurality of provided grooves may be provided on the road surface.

  Such a groove is generally called a “rain groove” and is carved for drainage on a paved road surface so that hydroplaning is unlikely to occur. In particular, it is often seen on highway with concrete pavement with a fine road surface, and it is normal that grooves of about 3mm in both groove width and groove depth are dug in the vehicle traveling direction at a pitch of 20-30mm. .

  The presence of this rain groove increases the tire slip resistance in the tire width direction, but may cause a groove wonder phenomenon in which the vehicle is swung sideways, resulting in a reduction in steering stability performance.

  One of the main causes is that the edge of the straight circumferential groove provided on the tire tread falls into the rain groove. When the edge of the circumferential groove falls into the rain groove, the edge of the straight circumferential groove is Bending, the contact pressure between the tire and the road surface is lost, and the lateral force (force in the tire width direction) changes, resulting in a groove wonder phenomenon in which the steering wheel is removed and the vehicle body fluctuates.

  For this reason, the proposal for improving RGW performance conventionally is made.

  For example, the circumferential groove is formed in a crank shape over the entire circumference in the tire circumferential direction so that the edge of the circumferential groove does not continuously fall into the rain groove, thereby suppressing the depression and improving the RGW performance. There is a proposal to improve (Patent Document 1).

  There is also a proposal for improving the RGW performance by chamfering the edge of the circumferential groove so that the edge of the circumferential groove does not fall into the rain groove (Patent Documents 2 and 3).

  Also, a plurality of sipes are formed on the vertical surface of the straight groove (the side wall surface of the groove) in the groove depth direction so as to reduce the force of collision between the rain groove edge of the road surface and the straight groove edge. There is a proposal to improve the RGW performance (Patent Document 4).

  Further, there is a proposal that the circumferential main groove is formed as a groove having a zigzag shape and continuously bent, thereby forming a structure generally called a point height (Patent Document 5).

  However, these proposals in Patent Documents 1-4, on the other hand, are reducing the function of the circumferential groove, particularly the edge portion, leading to a decrease in steering stability.

  Moreover, the proposal of patent document 5 can disperse | distribute and suppress the sudden change of lateral force which arises when a main groove edge falls into a rain groove by providing a point height, RGW performance can be improved. However, since the main groove is formed in a zigzag shape or a curved shape, the hydro-resistant performance is inferior to that of the straight groove.

JP 2009-6922 A JP-A-9-71106 JP 2009-6870 A JP-A-6-115317 JP 60-189607 A

  In view of the above points, an object of the present invention is to provide a pneumatic tire that is excellent in rain groove wander performance particularly during tire wear while suppressing a decrease in steering stability performance.

The pneumatic tire of the present invention that achieves the above-described object has the following configuration (1).
(1) In a pneumatic tire having a tread having a plurality of land portions defined by a plurality of circumferential straight grooves, a plurality of cuts in the tire width direction along at least one edge portion of the circumferential straight grooves A plurality of types of pitches having different cut widths W are disposed, and the narrow grooves satisfy the following (a), (b) and (c): A featured pneumatic tire.
(A) The maximum cutting width W _L is W _L <3.0 mm,
(B) {(maximum cutting width W _L ) − (minimum cutting width W _S )} ≧ 0.5 mm,
(C) Both the maximum cutting area and the minimum cutting area exist with respect to the contact length,

The pneumatic tire of the present invention preferably has any one of the following configurations (2) to (6).
(2) The total length of the circumferential direction of the maximum cutting area and the total circumferential length of the minimum cutting area are 30% or more with respect to the contact length, respectively. Pneumatic tire.
(3) The pneumatic tire according to (1) or (2), wherein the depth of the narrow groove is 90% or more of the maximum main groove depth.
(4) The pneumatic tire according to any one of the above (1) to (3), wherein among the plurality of types of pitches, there is a pitch in which a fine groove is not formed.
(5) The pneumatic tire according to any one of the above (1) to (4), wherein among the plurality of types of pitches, adjacent pitches have different cutting amounts.
(6) The pneumatic tire according to any one of (1) to (5), wherein the plurality of types of pitches are regularly arranged in a tire circumferential direction.

  According to the pneumatic tire of the present invention according to claim 1, in the pneumatic tire having a plurality of land portions partitioned by a plurality of circumferential straight grooves in the tread, along at least one edge portion of the circumferential straight grooves. In addition, a plurality of fine grooves cut in the tire width direction are formed, a plurality of types of pitches having different cut widths W of the fine grooves are disposed, and the fine grooves are formed in the above-described (a), ( By configuring the pneumatic tire so as to satisfy b) and (c), it is possible to disperse the falling of the edge of the straight circumferential groove into the rain groove, and good maneuvering with the pitch that is the minimum cutting width There is provided a pneumatic tire capable of achieving both maintenance of stability and improvement of RGW performance by a pitch which is the maximum cutting width.

  According to the pneumatic tire of the invention concerning Claims 2-6, the pneumatic tire which can improve more the RGW performance of the pneumatic tire of this invention concerning Claim 1, and can acquire a bigger effect reliably is provided. Is done.

(A), (b) is the top view which showed typically the principal part of the tread of the pneumatic tire concerning this invention, (a) and (b) are the things of the same form, (B) is a detailed explanation of the narrow groove portion in particular. It is the perspective view which showed the form of the narrow groove in the pneumatic tire concerning this invention. It is the side view which looked at the form of the narrow groove in the pneumatic tire concerning the present invention from the tire width direction.

  Hereinafter, the pneumatic tire of the present invention will be described in more detail.

The pneumatic tire of the present invention is a pneumatic tire having a plurality of land portions partitioned by a plurality of circumferential straight grooves in a tread, and is arranged in the tire width direction along at least one edge portion of the circumferential straight grooves. A plurality of types of pitches having different cut widths W are formed while forming a plurality of cut grooves, and the slots are as follows (a), (b) and (c) It is characterized by satisfying.
(A) The maximum cutting width W _L is W _L <3.0 mm,
(B) (maximum cutting width W _L ) − (minimum cutting width W _S ) ≧ 0.5 mm,
(C) Both the maximum cutting area and the minimum cutting area exist with respect to the contact length,

FIG. 1A is a plan view schematically showing a main part of a tread 1 of a pneumatic tire according to the present invention, and the tread 1 is partitioned by a plurality of circumferential straight grooves 2 (2A, 2B). It has several land parts. Each of the circumferential straight grooves 2A and 2B has edge portions 31, 32, 33, and 34 on both sides of the groove, respectively, and a plurality of fine grooves cut in the tire width direction along at least one of the edge portions. A plurality of types of pitches P (P _1i , P _2i , P _3i , P _4i ) that form the grooves 4 and have different cut widths W are arranged. In FIG. 1A, 5 is a lug groove (lateral groove), and 6 is a sipe. 7 is a center line (tire equator).

  In the present invention, as shown in FIG. 1B, the pitch P is any one of the edge portions 31, 32, 33, 34 on both sides of the circumferential straight groove 2 (2A, 2B). In all, it exists over the whole circumferential direction along each edge part, and a pitch is each divided | segmented by the lug groove (horizontal groove) 5 and the sipe 6. As shown in FIG.

In the present invention, at each edge portion, the pitches existing along the respective edges are arranged as a plurality of types of pitches having different cut widths W of the narrow grooves 4 for each pitch. If shown on the tire equator-side edge 31 of the circumferential straight groove 2A in FIG. 1B, P _1i (i is 1... N) is P ₁₁ , P ₁₂ , P ₁₃ ,. Are connected over the entire circumference in the tire circumferential direction, and the cut width W of the narrow groove 4 is different for each pitch.

  The cut width W of the narrow groove 4 may be zero, that is, there may be a pitch in which the narrow groove 4 is not formed, and the one shown in FIG. An example in which the pitch is not formed with a narrow groove is shown.

  It is preferable that 3 to 10 pitches exist on one edge, but basically the number of pitches is divided by lug grooves (lateral grooves) 5 and sipes 6 so that the pitch is formed. And is determined by the presence of Sipe. The plurality of types of pitches having different cutting widths W are not necessarily different from each other at all pitches, and are preferably about several types having substantially different values of about 0.5 mm.

  Further, the narrow groove 4 does not have to be formed on all edges (four in FIG. 1, 31, 32, 33, 34), and may be formed on at least one edge. Alternatively, for example, each circumferential straight groove may be formed on the outer edge in the tire width direction.

It is important that the narrow groove 4 is formed so as to satisfy the following three relationships (a), (b), and (c).
(A) The maximum cutting width W _L is W _L <3.0 mm,
(B) {(maximum cutting width W _L ) − (minimum cutting width W _S )} ≧ 0.5 mm,
(C) Both the maximum cutting area and the minimum cutting area exist with respect to the contact length,

  As described above, the pneumatic tire according to the present invention has a plurality of different pitches with different cut widths W of the narrow grooves, so that the positions of the narrow grooves in the tire width direction are constant. Therefore, it is possible to disperse the drop of the edge into the running rain groove, and even if the tire wear progresses, the narrow groove is smaller than the one where the position in the tire width direction is constant. The effect of providing can be maintained and exhibited better. In the case where the circumferential main groove is a zigzag groove, the drainage performance (hydro performance) is deteriorated, so it is not adopted in the present invention.

When the maximum cut width W _L of the thin groove 4 is greater than 3.0mm, the drop increases driving stability on that portion is reduced. Further, when the value of {(maximum cutting width W _L ) − (minimum cutting width W _S )} is less than 0.5 mm, the positions of the narrow grooves in the tire width direction are close, and the effect of dispersing the positions is obtained. Since it becomes scarce, it is not preferable.

  Moreover, in order to exhibit the effect of this invention satisfactorily, it is important that both the maximum cutting area and the minimum cutting area exist with respect to the contact length. Here, the maximum cut region refers to a region where the cut width W of the narrow groove is the largest pitch, and the minimum cut region refers to a region where the cut width W of the narrow groove is the smallest pitch. “Present to ground contact length” means that the pneumatic tire is filled with the air pressure corresponding to the maximum load capacity in the air pressure-load capacity correspondence table specified in the JATMA Yearbook (2011 edition). It is obtained by measuring the length in the tire circumferential direction (the length between the end positions in the circumferential direction at the edge portion) with the footprint when pressed against a flat surface with a load of 70% of its maximum load capacity. This means that there are at least both the maximum cutting area and the minimum cutting area in the ground contact length. This is important in obtaining the effects of the invention. As a result, when the tire is in contact with the ground, both the maximum incision area and the minimum incision area are in contact with each other at the same time, so that the effect of the position of the narrow groove in the tire width direction being not constant is remarkably exhibited. It is because it can be made.

  In particular, the total of the circumferential lengths of the maximum cutting area and the circumferential length of the minimum cutting area is preferably 30% or more with respect to the contact length. If any of them is less than 30%, the above-described dispersion effect tends to be small, which is not preferable.

  Further, the depth of the narrow groove 4 is preferably 90% or more of the maximum groove depth of the circumferential straight groove, and if it is less than 90%, the effect of providing the narrow groove is reduced, which is not preferable. By setting it to 90% or more of the maximum groove depth of the groove, it becomes possible to maintain the rain groove wandering performance even when the tire is worn.

  As described above, there may be a pitch in which the fine groove is not formed. Rather, since there is a pitch in which the fine groove is not formed, there is a pitch of the fine groove between the fine groove and the pitch. It can be said that the positions in the width direction are surely different from each other, and the effect of the present invention becomes remarkable, which is preferable.

  In addition, it is preferable that the adjacent pitches have different cut amounts among a plurality of types of pitches provided on one edge, and the effect of the present invention becomes clearer.

  In addition, it is preferable that the plurality of types of pitches are regularly arranged in the tire circumferential direction, and by doing so, the effects of the present invention can be reliably obtained, and further, the progress and effect of the wear can be improved. It is preferable because the size relationship can be predicted.

  The narrow groove 4 preferably has a width C (FIG. 2) in the tire circumferential direction of 0.5 to 2.0 mm. When the width C of the narrow groove 4 is in the range of 0.5 to 2.0 mm, the rigidity of the edge portion becomes optimum, and the RGW performance can be further improved. More preferably, the width C is 1.0 to 1.5 mm.

  Furthermore, it is preferable that the space | interval t (FIG. 2) between the adjacent narrow grooves 4 shall be the range of 1.0-10.0 mm. When the distance t between adjacent narrow grooves 4 is in the range of 1.0 to 10.0 mm, it is easy to adjust the rigidity of the edge portion to achieve the optimum, and realize better RGW performance. It is easy to do. A more preferable interval t is 4.0 to 7.0 mm.

  In addition, as shown in FIGS. 2 and 3, the narrow groove 4 has a land surface with an inclination angle θ of 10 ° to 80 ° with respect to the tire radial direction on a cross section perpendicular to the tire rotation axis. It is preferable to drill from the (tread 1) to the tire inner surface side. This is because if the narrow groove is formed with an inclination angle, the rigidity of the edge portion can be lowered and the RGW performance can be further improved. The most preferable inclination angle θ is 30 ° to 60 °.

Examples 1-4, Comparative Examples 1-4, Conventional Example 1
The tire size is 225 / 65R17, and the ratio (%) of the size of the cut width W of the narrow groove 4 and the total of the circumferential length of the maximum cutting area and the total circumferential length of the minimum cutting area are changed. A total of eight types of tires of Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention were prepared, and a test tire was manufactured by assembling a rim on a wheel having a rim size of 17 × 6.5 and filling with air at an air pressure of 220 kPa. did. Conventional Example 1 and Comparative Example 1 are examples in which no narrow grooves are provided, and Comparative Example 2 is an example in which continuous chamfered portions are provided.

  The tread pattern of each test tire is the same as that shown in FIG. For the circumferential grooves, Examples 1 to 4 and Comparative Examples 1 to 4 were all similar straight grooves, and in Conventional Example 1, the circumferential grooves were zigzag grooves (so-called point heights). In Comparative Example 2, the shape of the edge portion of the main groove is chamfered, but the chamfered block and the block without any chamfer or fine groove are alternately arranged (special feature). A mode described in Japanese Unexamined Patent Publication No. 2008-230357. The chamfering width is 1.5 mm as described in the narrow groove cutting width column of Table 1, and the chamfering depth is 4.0 mm as described in the narrow groove depth column of Table 1. did.

  The circumferential straight groove 2A (main groove width 9.0 mm) is provided at a distance of 17.0 mm from the tire equator, and the circumferential straight groove 2B (main groove width 8.0 mm) is 50.5 mm from the tire equator. Provided in position. The distance between the center line and the ground contact is 82.5 mm.

  Each test tire was mounted on a domestic SUV (Sport Utility Vehicle) vehicle (FF drive system), and RGW evaluation, steering stability, and hydro performance were evaluated by the following methods.

The evaluation results for each are shown in Table 1. According to the present invention, it can be seen that the steering stability, the RGW performance, and the hydro performance are all excellent.
(1) RGW evaluation:
It traveled on the rain groove road (test course), and the feeling evaluation about RGW property was performed, and it indexed and evaluated. The evaluation was performed by index evaluation with one comparative example as 100, and the larger the value, the better.
(2) Evaluation of handling stability:
A driving test was performed on the circuit (test course), and a feeling evaluation about the handling stability was performed. The evaluation is performed by index evaluation with one comparative example as 100, and the larger the value, the better.
(3) Evaluation of hydro performance:
A straight hydroplaning performance test path (test course), water generation speed is measured at a water depth of 10 mm, and an index evaluation is performed with a circumferential straight groove (Comparative Example 1) as 100, and the larger the value, the better.

1: tire tread 2, 2A, 2B: circumferential straight groove 31, 32, 33, 34: edge portion 4: narrow groove 5: lug groove (lateral groove)
6: Sipe 7: Center line (tire equator line)
P, P _1i , P _2i ......: Pitch,
W, W _1i , W _2i ......: Cut width of narrow groove 4 W _L : Maximum cut width W _S : Minimum cut width C: Circumferential width of narrow groove 4 θ: Cut angle of narrow groove 4 t: Adjacent Spacing between narrow grooves 4

Claims (6)

In a pneumatic tire having a plurality of land portions partitioned by a plurality of circumferential straight grooves in a tread, a plurality of narrow grooves cut in the tire width direction along at least one edge portion of the circumferential straight grooves And a plurality of types of pitches having different cut widths W of the fine grooves, and the fine grooves satisfy the following (a), (b) and (c): Pneumatic tire.
(A) The maximum cutting width W _L is W _L <3.0 mm,
(B) {(maximum cutting width W _L ) − (minimum cutting width W _S )} ≧ 0.5 mm,
(C) Both the maximum cutting area and the minimum cutting area exist with respect to the contact length,   2. The pneumatic tire according to claim 1, wherein a total of a circumferential length of a maximum cutting area and a circumferential length of a minimum cutting area is 30% or more with respect to the contact length, respectively.   The pneumatic tire according to claim 1 or 2, wherein a depth of the narrow groove is 90% or more of a maximum main groove depth.   4. The pitch according to any one of claims 1 to 3, wherein there is a pitch in which a narrow groove is not formed among the plurality of types of pitches. Pneumatic tire.   The pneumatic tire according to any one of claims 1 to 4, wherein, among the plurality of types of pitches, the depth of cut differs between adjacent pitches.   The pneumatic tire according to claim 1, wherein the plurality of types of pitches are regularly arranged in a tire circumferential direction.

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