JP2002036819A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radial tire capable of preventing the side part of a land from premature wear, enhancing the maneuvering stability and wet performance, and suppressing the increase in the rolling resistance. SOLUTION: Mutually confronting inside corners 7, 8, 9, 10 of ribs 4, 5, and 6 are chamfered in accordance with the grounding lengths in the tread grounding area of the rib edges Q1, Q2, Q3, Q4 positioned apart from each other with the circumferentially stretching main grooves 2 and 3 interposed, and the products of the widths L1, L2, L3, L4 in the direction across the land width of the chamfers and the depts H1, H2, H3, H4 in the tire radial direction are related to the respective grounding lengths, and the chamfered side parts of the lands 4, 5, and 6 are equipped with thin grooves cut in across the land widths, opening in the land side-wall 5a, and stretching in the direction of the main groove bottom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a tread pattern based on a land portion, for example, a rib, which is divided by a circumferential groove provided on a tread tread surface, and is applied to vehicles such as passenger cars, buses and trucks. It is related to pneumatic tires, in particular, while changing the cross-sectional shape of the rib from the conventional shape according to the shape of the contact area of the tread tread,
By providing a narrow groove on the side of the rib that faces the width direction of the rib, the steering stability for dry and wet treads is improved under excellent wear characteristics, and rolling resistance is also reduced. It is an improvement.

[0002]

2. Description of the Related Art When a tire provided with a circumferential groove on a tread tread contacts the road surface and rolls while supporting a load,
It is known that a land portion separated by the circumferential groove, for example, a side portion of the rib is subjected to a large widthwise shear strain as compared with a center portion of the rib, and this land portion is not slid to the side portion of the rib. It is known that such concentration of strain causes an increase in rolling resistance, a decrease in wet performance, a decrease in steering stability, and the like, and also causes abnormal wear in which the strain concentration portion is worn particularly early.

[0003] For this reason, it has been proposed to solve the above problem by forming the side portion of the rib into a convex curved surface and suppressing the concentration of strain there. Depending on the particular method of the convex surface, on the contrary, premature wear of the side portion of the rib becomes more severe, and as a result,
There was a problem that steering stability, rolling resistance, and the like deteriorated.

An investigation into the cause of this early wear revealed that uneven wear that occurred when the side portions of the ribs were formed into a convex curved shape was caused by the fact that the contact length of the side portions of the rib was reduced by the difference in diameter. It has been found that this is due to the fact that the side portion is dragged against the road surface and a large circumferential shear deformation is generated at the side portion thereof because it is shorter than the ground contact length of the other portion.

[0005]

With this in mind,
The applicant previously described the shape of the side portion of the rib on the opposite side of the same rib mainly for the purpose of preventing early wear of the side portion of the rib with respect to the tire input during the straight running of the vehicle. A pneumatic tire determined based on the relationship with the side, the relationship with the side of the rib separating the groove, and the relationship with the ground contact shape was proposed as Japanese Patent Application No. 2000-105467.

By the way, in consideration of steering stability when the vehicle turns on a curved road or the like, in turning, a larger lateral shear strain due to the turning lateral force is concentrated on the side portion of the rib. Therefore, if the distortion is to be reduced only by the applicant's earlier proposed technology, the side portions of the ribs need to have a more rounded cross-sectional shape. There has been a problem that early wear of the side portion of the rib due to the diameter difference is inevitable.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and effectively prevents early abnormal wear of a side portion of a land portion in both straight traveling and turning traveling of a vehicle. Another object of the present invention is to provide a pneumatic tire capable of significantly improving steering stability and wet performance, and effectively suppressing an increase in rolling resistance.

[0008]

A pneumatic tire according to the present invention includes at least one main groove formed on a tread surface and extending continuously in a circumferential direction, and a land portion defined by the main groove. In accordance with the contact length of each land edge located across the main groove in the tread contact area, chamfering is performed on each of the mutually opposing corners of each land. In the case, the product of the width in the land width direction and the depth in the tire radial direction of each chamfered portion is defined as a magnitude relationship corresponding to each of the contact lengths, for example, when the contact lengths are equal. Shall make the respective products equal, on the other hand, when the contact length of one side is longer than that of the other side, make the product on one side larger than the product on the other side, and furthermore, To the width of the land on the chamfered side Thereby opening the land portion side wall facing, in which the thin groove extending in the main groove bottom direction, is provided at intervals in the tread circumferential direction.

The area of the interview here is JATMA YEAR
It refers to the contact area when the maximum load capacity is loaded under the filling of the maximum air pressure specified in BOOK.

[0010] In this pneumatic tire, the technique disclosed in Japanese Patent Application No. 2000-105467 based on the earlier proposal of the applicant, that is, more specifically, the respective land portions that separate the main groove are opposed to each other. At the corners, the technology of chamfering the magnitude relationship of the ground contact length at each land edge, the magnitude relationship of the product of the width of the chamfer in the land portion width direction and the height of the tire in the radial direction is matched. On the basis of this, the rubber was removed from the portion that caused the shear strain in the width direction in the input in the straight-ahead state, and the chamfering was performed so as to effectively reduce the shear strain in the width direction while suppressing early abrasion due to the diameter difference in the straight-ahead state. However, a narrow groove opening in the land portion side wall is provided in the land portion side portion by engraving in the width direction of the land portion, and the rubber in this portion is removed to generate a lateral force at the time of turning without changing the ground contact length. Even greater transverse shear And thereby effectively prevent circumferential shearing force due to the difference in ground contact length, which occurs when a large widthwise shearing strain due to lateral force is absorbed only by chamfering. In addition, it is possible to reduce the shear strain in the width direction at the time of the lateral force, secure high wear performance regardless of whether the vehicle is going straight or turning, and effectively improve the rolling resistance, the wet performance, and the steering stability.

Preferably, the extension length of the narrow groove in the tire radial direction is set to 0.6 to 0.9 times the depth of the main groove, and preferably, the opening width of the narrow groove is set to 0.1. 5 to 2.5 mm.

If the extension length of the narrow groove is less than 0.6 times, the amount of rubber to be removed is small, so that the distortion cannot be sufficiently reduced. Then, the narrow groove disappears. On the other hand, when it exceeds 0.9 times, the rigidity of the land portion in the circumferential direction is insufficient, and early wear occurs in the land portion provided with the narrow groove.

If the opening width of the narrow groove is less than 0.5 mm, the amount of rubber to be removed is too small.
Since the contact area on the side portion of the land is reduced and the contact pressure is increased, premature wear occurs there.

The depth of the narrow groove in the land width direction is preferably in the range of 1 to 2 mm. If it is less than 1 mm, the amount of rubber to be removed is too small, and if it exceeds 2 mm, the contact area of the land side portion becomes too small.

Further, it is preferable that the arrangement pitch of the narrow grooves is in the range of 5 to 30 times the narrow groove opening width. That is,
If it is less than 5 times, the contact area becomes too small and 30
If it exceeds twice, the amount of rubber to be removed is too small.
It is difficult to ensure the effect of providing the narrow groove.

[0016]

FIG. 1 is a cross-sectional view in the tread width direction showing a tread half according to an embodiment of the present invention. That is, in each half of the tread tread 1, two main grooves 2 and 3 extending linearly and continuously in the tread circumferential direction are provided, respectively, and these main grooves 2 and 3 allow the respective side portions thereof to be formed. The ribs 4,5,6 are sectioned at the corners, and the corners 7,8,9,10 of the ribs 4,5,6 facing each other across the main grooves 2,3 are chamfered. And the respective chamfered surfaces 7a, 8a, 9a, 1
0a is a curved surface that is convex outward.

In performing such chamfering, here, the tread tread surface contact area of the rib edges Q1, Q2, Q3, Q4 of the ribs 4, 5, 6 before chamfering, which are located across the main groove. , Ie, the respective ground lengths Q1L, Q2L, Q when the maximum load capacity is loaded
3L and Q4L are obtained in advance, and, for example, when the respective lengths are equal, the respective widths L1, L2, L of the respective chamfered portions measured in the land width direction.
3, L4, the length to the rib edges Q1, Q2, Q3, Q4 in the figure and the depths H1, H2, H3, H measured in the radial direction.
4. In the figure, the respective products L1 × H1, L2 × H2, L3 × H3 and the depths from the rib edges Q1, Q2, Q3, Q4.
Each width L is set such that L4 × H4 is equal to each other.
1, L2, L3, L4 and depth H1, H2, H3, H
Select 4. Here, the grounding lengths Q1L, Q2L,
If there is a difference between Q3L and Q4L, the respective dimensions are determined according to the length of the respective grounding lengths so that the above-described products become larger or smaller.

Here, as shown in FIG. 2 by taking one rib 5 as an example, the rib 5 is cut into the chamfered side portion in the width direction of the rib 5 to form a rib side wall 5a. Opening narrow grooves 11 and 12 are provided extending in the groove bottom direction of the main grooves 2 and 3, and preferably, as shown in a partially enlarged sectional view of FIG. The extension length L in the radial direction is set to a range of 0.6 to 0.9 times the main groove depth H. And preferably, the depth D of the narrow grooves 11 and 12 in the rib width direction is set to 1 to 2 mm.

As shown in FIG. 4, the narrow grooves 11 and 12 are preferably formed so that the opening width w is in the range of 0.5 to 2.5 mm. Is preferably formed so that the arrangement pitch P is in the range of 5 to 30 times the opening width w.

According to the tire configured as described above,
As described above, the chamfered portion can sufficiently exhibit its original function of reducing the shear strain in the width direction. Effective prevention based on the distortion reduction function can advantageously improve the steering stability and the wet function, and also effectively prevent an increase in rolling resistance.

Although the embodiment of the present invention has been described with reference to the case where all the ribs are chamfered, as shown in FIG. 5A, one or more ribs which are not chamfered are left in the tread half. As shown in FIGS. 5B and 5C,
Chamfering only the rib on one side of the main groove, or
As shown in FIG. 6 (a), one or more ribs that are not chamfered are left on the entire tread portion. As shown in FIG. 6 (b), one or more ribs are present in the tread portion. It is also possible to chamfer only the ribs or, as shown in FIG. 6C, to chamfer only the ribs on either side of the main groove in the entire tread portion. Also, instead of using the land as a rib, a block pattern having a lug groove may be used.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a tire for trucks of size 11R22.5 in which four circumferential main grooves are formed symmetrically on the tread tread surface, the conventional tire 1 is such that the contour of the rib coincides with the contour of the tread tread. The conventional tire 2 has L1 × H1 <L2 × H2 under the relationship of Q1L <Q2L <Q3L <Q4L, with no chamfer and no narrow groove. <L3 × H3 <L4
The corners of each of the ribs were chamfered so as to be × H4, and the conventional tire 3 had a narrow groove provided on the side of each rib of the conventional tire 1. Table 1 shows specific numerical values of the conventional tire 2.

For these tires, a second rib (FIG. 1)
Each of the example tires and the comparative tires having the rib 5) according to the present invention had the structure shown in Table 2. The structure of the chamfer was the same as that of the conventional tire 2. Each of these tires was mounted on a 7.5 × 22.5 rim, and the rolling resistance test, the uneven wear drum test and the wet lateral force test were performed under the conditions of a charged air pressure of 700 kPa and a load of 25.0 kN. Of each. Table 3 shows the results.

The values indicated as indices in Table 3 assume that the value of the conventional tire 1 is 100. The smaller the rolling resistance value is, the smaller the resistance value is, which is advantageous for fuel saving. The uneven wear ratio is the ratio of the amount of wear on the rib side portion (larger side) of the second rib to the amount of wear on the rib center, and the closer this value is to 1.0, the more uniform the wear.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

According to Table 3, the rolling resistance, uneven wear and wet lateral force of the conventional tire 2 in which only the chamfer is provided at the corner of the rib and the conventional tire 3 in which only the narrow groove is provided in the side portion of the rib. Although each is effective, it can be seen that the example tires using the two techniques are more effective in rolling resistance and wet performance without deteriorating the uneven wear ratio.

On the other hand, as a result of examining the length, opening width, depth and arrangement interval of the narrow grooves using comparative tires 1 to 8, when those values are out of the range specified in the claims, Indicates that the above effect is relatively reduced.

[0030]

As described above, according to the present invention, the cornering of the land portion and the narrow groove provided in the side portion of the land portion can provide the steering stability and wet performance without premature wear of the chamfered portion. , And an increase in rolling resistance can be advantageously prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in the width direction showing a tread half according to an embodiment of the present invention.

FIG. 2 is a perspective view of one rib.

FIG. 3 is an enlarged sectional view of a narrow groove.

FIG. 4 is a perspective view showing a narrow groove.

FIG. 5 is a cross-sectional view in a width direction showing a tread half according to another embodiment.

FIG. 6 is a cross-sectional view in a width direction showing still another embodiment.

[Explanation of symbols]

 Reference Signs List 1 tread surface 2,3 main groove 4,5,6 rib 5a rib side wall 7,8,9,10 corner 7a, 8a, 9a, 10a chamfer surface 11,12 narrow groove Q1, Q2, Q3, Q4 rib edge L1 , L2, L3, L4 Width H1, H2, H3, H4 Depth L Extension length H Main groove depth D Depth w Opening width P Arrangement pitch

Claims (5)

[Claims] A main groove formed on the tread tread surface and extending continuously in a circumferential direction; and a land portion divided by the main groove, and a tread surface contact of each land portion edge located across the main groove. Depending on the ground contact length in the area, chamfers are made on the opposite corners of each land, and the product of the width of each chamfer in the land width direction and the depth in the tire radial direction is calculated. , And a magnitude relationship corresponding to each of the contact lengths,
The land portion, on the chamfered side portion, is opened in the land portion side wall facing the width direction of the land portion, and narrow grooves extending in the bottom direction of the main groove are provided at intervals in the tread circumferential direction. Become a pneumatic tire. 2. The pneumatic tire according to claim 1, wherein the extension length of the narrow groove in the tire radial direction is 0.6 to 0.9 times the depth of the main groove. 3. The pneumatic tire according to claim 1, wherein the narrow groove has an opening width of 0.5 to 2.5 mm. 4. The pneumatic tire according to claim 1, wherein the depth of the narrow groove in the land width direction is 1 to 2 mm. 5. The arrangement pitch of the narrow grooves is set to 5 to 5 times the opening width of the narrow grooves.
The pneumatic tire according to any one of claims 1 to 4, which is 30 times as large.