JPS61291204A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To obtain a strong road holding, by providing a main groove, both side portions and slits at a tread portion, specifying a ratio of the sum of widths of the both side portions to a width of the tread portion, and also specifying a ratio of an area of grooves formed in the both side portions to a total area of the both side portions. CONSTITUTION:A tread portion 2 consists of a central portion 10 and a wide both side portions 11 connected with the central portion 10. The central portion 10 is formed with at least two wide main grooves 13 and narrow sub grooves 14 on the equatorial plane, both grooves 13 and 14 extending circumferentially of a tire. The both side portions 11 are formed with lateral grooves 15 extending in a direction of a rotating shaft of the tire. The sum (W11+W11) of widths of the both side portions 11 is set to 35-65% of a width W2 of the tread portion 2, and an area of the lateral grooves 15 in the both side portions 11 is set to 5-20% of a total area of the both side portions 11. Further, the both side portions 11 are formed with lateral slits 17a and circumferential slits 17b extending straight like a lattice.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a pneumatic radial tire, for example, a trend in tires with so-called high-performance, high-grip properties that have excellent handling stability and road grip performance during driving. This invention relates to a pneumatic radial tire with improved road surface pattern.

(Prior Art) Conventionally, there are pneumatic radial tires with high performance and high grip properties, such as those shown in Figs. 4 and 5. Fig. 4 shows one of the conventional pneumatic radial tires. FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 4.

In FIGS. 4 and 5, 31 is a pneumatic radial tire, and the pneumatic radial tire 31 has a tread portion 32 that covers the surface of its outer periphery, and a tread portion 32 that covers the surface of the outer periphery and both ends 32a of the tread portion 32 in the tire rotation axis direction. It has a connecting shoulder portion 33 and a belt portion 34 formed on the radially inner side of the tread portion 32 over substantially the entire width of the tread portion 32. At least two steel cord layers having sufficient strength are arranged in the belt portion 34 so as to cross each other, giving the tread portion 32 high rigidity. The tread portion 32 consists of a center portion 36 and side land portions 37 connected to both sides of the center portion 36, and the side land portions 37 extend from the ends of the wide main grooves 38 provided at both ends of the center portion 36 to both ends 32a of the trend portion 32. It forms a wide range of ridges (the figure shows the addition of minor grooves, which will be described later). Since the surface portion 39 of the ridge portion of the side land portion 37 has a wide contact area with the road surface, it is expected that a strong road grip force will be generated due to the frictional resistance with the road surface. However, since the rigidity of the belt portion 34 is too high,
The ridge surface portion 39 of the side land portion 37 cannot apply effective ground pressure to the road surface. Therefore, as shown in FIGS. 4 and 5, in the side land portion 37, a lateral groove 41 extending long in the direction of the rotation axis, a short branch groove 42, and a minor groove 43 having a narrow width in the circumferential direction are provided. It is designed to improve ground contact performance and drainage performance in rainy weather.

(Problems to be Solved by the Invention) However, although sufficient ground contact performance and drainage performance can be obtained by forming the lateral grooves 41, branch grooves 42, and sub-grooves 43 in the side land portion 37, on the other hand, For this reason, within the side land portions 37, the effective actual ground contact area that actually contacts the road surface is reduced by the groove area, and the road gripping force of the side land portions 37 without these grooves is reduced by the amount of this groove area. Road grip is reduced.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a pneumatic radial tire that has strong road grip performance during high-speed driving while sufficiently maintaining ground contact performance, drainage performance in rainy weather, and road grip performance. With the goal.

(Means for Solving the Problems) A pneumatic radial tire according to the present invention is a pneumatic radial tire having a trend section, in which at least two radial tires are formed in the center of the tread section so as to extend in the circumferential direction of the tire. a wide main groove; at least two side land portions adjacent to the main groove and continuous in the tire circumferential direction on both sides of the tread portion;
A notch formed in the side land portion substantially in the direction of the rotational axis of the tire and in the circumferential direction of the tire and in a lattice shape,
It is characterized in that the sum of the widths of the side land portions is 35 to 65% of the width of the tread portion, and the ratio of the area of the grooves in the side land portions to the total area of the side land portions is 5 to 20%. Moreover, it is preferable that the number of cuts in the rotation axis direction of the tire is 3 to 8 in the ground contact surface when a load is applied.

Further, the depth of the cut is 50% of the depth of the adjacent main groove.
% or more is preferable.

Here, the sum of the widths of the side land parts is 35 to 65 of the width of the tread part.
% is because if it is less than 35%, the rigidity of the side land part is small.
The total area is small, and sufficient road grip cannot be obtained. Also,
If it exceeds 65%, the groove area of the entire trend portion will be insufficient, resulting in insufficient drainage performance on rainy days and insufficient road grip on a wet road surface.

The reason why the ratio of the area of the grooves in the side wall to the total area of the side land is 5 to 20% is because if it is less than 5%, the rigidity of the trend part will become too large and the ground contact performance will be insufficient. The area is small and drainage performance during rainy days is insufficient. If it exceeds 20%, the effective actual ground contact area of the tread portion in contact with the road surface becomes too small, resulting in insufficient road gripping power.

Moreover, it is preferable that the number of cuts in the direction of the rotation axis is 3 to 8 within the ground contact surface when a load is applied. Further, the depth of the cut is desirably at least 40% or more, and preferably 50% or more, of the depth of the adjacent main groove.

Further, the thickness of the cut is such that both wall surfaces of the cut are in contact with each other within the ground contact surface where the tread portion contacts the road surface when a load is applied.

Here, the reason why the thickness of the notches is set to the extent that they touch each other under the ground contact surface is that although the depth of the cuts improves ground contact performance, below the ground contact surface, reducing the groove width due to the cuts to zero improves road grip performance. This is because it makes you

In addition, arranging the cuts in a grid pattern allows cuts to be made in any pattern regardless of the tread pattern, and arranging them in the rotational axis direction and circumferential direction improves ground contact performance. This is because it is suitable.

(Function) The trend part is provided with at least two wide main grooves extending in the tire circumferential direction, and the side land part adjacent to the main grooves is provided with cuts that are linear in the tire rotational axis direction and in the tire circumferential direction. Moreover, it is formed in a grid shape. Therefore, even if the trend portion becomes soft due to the cutting and the belt portion has high rigidity, the ground contact performance of the tread portion and road surface grip in rainy weather are sufficient. Further, the sum of the widths of the side land portions is 35 to 65% of the width of the trend portion, and the ratio of the area of the groove to the total area within the side land portions is 5 to 20%. Therefore, the effective actual ground contact area is large. Therefore, the generation of lateral force and road gripping force during high-speed running are exerted by almost the total area of the side land portions, resulting in extremely excellent steering stability and strong road gripping performance.

(Example) Hereinafter, an example of a pneumatic radial tire according to the present invention will be described based on the drawings.

1 and 2 are diagrams showing an embodiment of a pneumatic radial tire according to the present invention, and FIG. 1 is a partial plan view thereof.

First, the configuration will be explained.

In FIG. 1 and FIG. 2, 1 is a pneumatic radial tire, and the pneumatic radial tire 1 has a tread portion 2 covering the surface of its outer periphery, and a tread portion 2 at both ends 2a of the tread portion 2 in the tire rotation axis direction. Connecting shoulder part 3;
A belt portion 4 is formed on the radially inner side of the tread portion 2 over substantially the entire width of the trend portion 2. Further, a carcass portion 6 is formed on the radially inner side of the belt portion 4 and extends over a pair of bead portions 7 . The tire size of this example is 205/60 R15, and the internal structure other than the tread pattern on the trend part and part of the shoulder is a normal radial structure, so only the necessary details will be explained.
Detailed explanation will be omitted. For the carcass portion 6, polyester cord 1500 d/2 is used. The belt portion 4 uses two layers of 1×5 steel cords and is formed so as to intersect with each other at an angle of 18 degrees with respect to the circumferential direction.

The trend part 2 consists of a central part 10 and wide side land parts 11 connected to both sides of the central part 10, and the central part 10 has at least two (two in this embodiment) wide main grooves 13 and two wide main grooves 13. , a narrow sub-groove 14 is formed on the equatorial side of the main a13 so as to extend substantially in the tire circumferential direction. Horizontal groove 1 in side land part 11
5 is provided in the direction of the rotation axis of the tire. A lateral groove 16 is provided in the shoulder portion 3 in the direction of the rotation axis of the tire and connected to the lateral groove 15 of the side land portion 11. Both side ribs 1
The sum of the widths in the tire rotational axis direction of No. 1 (Wl□+W11) is 35 to 65% of the width W2 of the tread portion 2 in the tire rotational axis direction.
(58% in this example). Here, if it is less than 35%, the width of the side land portion 11 is narrow, the rigidity of the side land portion 11 is reduced, and sufficient road gripping force cannot be obtained. Moreover, if it exceeds 65%, the groove area of the entire tread portion 2 will be insufficient, the drainage performance will deteriorate in rainy weather, and the road surface grip on a wet road surface will deteriorate.

Further, the ratio of the area of the lateral groove 15 in the side land portion 11 to the total area of the side land portion 11 is 5 to 20% (10% in this embodiment).
It is. If it is less than 5%, the rigidity of the side land portion 11 increases,
Furthermore, the rigidity of the belt portion 4 is added, and the distribution of ground pressure on the tread portion 2 becomes worse. If it exceeds 20%, the effective ground contact area in contact with the road surface becomes too small, resulting in insufficient road surface grip.

Reference numeral 17 denotes a notch, and the notch 17 is formed in the side land portion 11 by a notch 17a substantially in the direction of the tire rotational axis and a notch 17b in the circumferential direction of the tire, which are linearly formed in a lattice shape.

The number of notches 17a in the tire rotation axis direction is arranged so that there are four in the tire contact patch with the road surface when a load is applied.

The depth I)+t of the cut 17 is 40% or more (80% in this example) of the groove depth DI3 of the adjacent main groove 13.

If it is less than 40%, sufficient ground contact performance cannot be obtained. Further, the thickness WI of the notch 17 is 1n, and the facing side walls 17C of the notch 17 are in contact with each other under the tire contact surface.

Next, the effect will be explained.

When driving on a dry road surface or a wet road surface in rainy weather, in the pneumatic radial tire of the present invention, the width Wl+ of the side land portion 11 is as wide as 58% of the width W2 of the tread portion 2, and
The side land portion 11 has a notch 17 with which the side wall contacts under the ground contact surface.
Because of this, sufficient ground contact performance can be obtained even if the belt portion 4 has high rigidity, and the road surface grip is also sufficient, resulting in extremely excellent steering stability performance and road surface grip performance during high-speed driving. . In addition, the central part 10 has a wide main groove 13, and the side land part 11 has a lateral groove 15 whose groove area is 5%.
In addition to the above, since there is also a grid-like cut, the drainage performance of rainwater is sufficient, and the road surface grip performance on a wet road surface is sufficiently maintained.

Next, an example and two comparative examples, that is, three types of test tires (tire A of the present invention, comparative tire B, and conventional tire C) were manufactured and tested to confirm the effects of the present invention. do.

The tire size of the test tire was 205/60R15, and it was a normal radial tire with a steel belt in the belt section. The tire A of the present invention according to the embodiment has the same structure as the embodiment described above (FIGS. 1 and 2). In addition, as shown in FIG. 2, the comparative tire B (numbered 20) of Comparative Example 1 has a configuration in which the notch 17 is removed from the tire A of the present invention of the example, and is given the same reference numeral as the example. Therefore, detailed explanation will be omitted.

As shown in FIG. 3, the conventional tire C of Comparative Example 2 has the same configuration as the conventional tire described above, and detailed description thereof will be omitted.

The three experimental tires were manufactured in the same manner, four each, using the same materials. These test tires were alternately mounted on a test vehicle to perform a driving performance test, and an indoor test using a testing machine was also performed to compare the performance. Performance tests were conducted on road grip performance on dry roads, road grip performance on wet roads in rainy weather, ground contact performance, and groove area ratio. Road grip performance on a dry road surface was tested by driving a test vehicle around a lap course at high speed. In addition, a slalom running test was conducted on a wet road surface to test road grip performance. Ground contact performance was determined by comparing the theoretical ground contact area and the actual ground contact area.

The test results are shown in the table below. In the following table, the test results are expressed as an index with Comparative Tire B set as 100, and the larger the value, the better. The groove area ratio is the ratio of the measured value to the theoretical value, expressed as a percentage.

As shown in the table above, the tire A of the present invention of the example is extremely superior to Comparative Examples 1 and 2 in road grip performance on a dry road surface. Furthermore, both the road surface gripping performance and ground contact performance on a wet road surface in rainy weather are almost the same as the conventional tire C of Comparative Example 2, and the performance is significantly higher than that of Comparative Example 1 where there is no notch in the side land area. is improving.

(Effects of the Invention) As explained above, according to the present invention, the road grip performance during high-speed driving is significantly improved while the ground contact performance and road grip performance on wet roads in rainy weather are sufficiently maintained. can.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an embodiment of a pneumatic radial tire according to the present invention, and FIG. 1 is a partial plan view thereof,
FIG. 2 is a sectional view taken along the line nn in FIG. 1. FIG. 3 is a partial plan view of a comparative tire for confirming the effects of the present invention. 4 and 5 are diagrams showing a conventional tire, with FIG. 4 being a partial plan view thereof, and FIG. 5 being a sectional view taken along the line V-V. 1------1...Pneumatic radial tire, 2...
---One tread part, 3----------- Shoulder part, 10-- Central part, 11-- One side land part, 13-------- Main groove , 17--Depth of cut, DI 3-----Depth of groove, DI? --- Depth of cut: W t --------- Width of tread portion, W, --111111 Width of side land portion.

Claims (3)

[Claims] (1) In a pneumatic radial tire having a tread, at least two wide main grooves are formed in the center of the tread to extend in the circumferential direction of the tire, and at least two wide main grooves are formed in the center of the tread to extend in the tire circumferential direction, and At least two side land portions continuous in the tire circumferential direction, and cuts formed in the side land portions in a lattice shape substantially linearly in the tire rotational axis direction and in the tire circumferential direction, and the width of the side land portions is A pneumatic radial tire characterized in that the sum of the widths of the tread portions is 35 to 65% of the width of the tread portion, and the ratio of the area of the grooves in the side land portions to the total area of the side land portions is 5 to 20%. (2) The pneumatic radial tire according to claim (1), wherein the number of cuts in the rotational axis direction of the tire is 3 to 8 in the ground contact surface when a load is applied. (3) The depth of the cut is 40% of the depth of the adjacent main groove
A pneumatic radial tire according to claim (1), characterized in that the above exists.