JPH069921B2 - Radial tires for high-speed running on heavy roads - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radial tire for high-speed running on a good road capable of reducing abnormal wear such as shoulder wear without impairing wet grip performance.

[Conventional technology]

Generally, in radial tires for trucks and buses, the tread portion through which the carcass using the steel cords of the radial arrangement passes is reinforced by a belt layer using three or more belt plies made of steel cords to increase the rigidity of the tread portion. Therefore, it is superior in wear resistance, fuel economy, cut / puncture resistance and easiness of rehabilitation compared to the bias tire, but the tread of the tread does not wear evenly depending on usage conditions, so-called Abnormal wear such as shoulder wear is likely to occur.

Due to this local premature wear, the maneuverability of the tire is impaired, which often leads to early replacement of the tire for safety. Similarly, due to this local wear, the tire cannot be rehabilitated, resulting in poor economic efficiency.

In order to improve such shoulder drop wear, conventionally, (1) the crown flatness value defined by a value obtained by dividing the radius of curvature of the tread in the meridional section of the tire by the sectional width of the tire is increased to increase the tire crown portion. And the outer diameter difference of the shoulder part should be small.

(2) To widen the width of the belt layer between the carcass cord and the tread rubber to increase the rigidity of the shoulder portion.

And so on.

However, the former method reduces the slippage of the shoulder part peculiar to radial tires to mitigate the acceleration of wear due to slippage. In this respect, the effect of suppressing shoulder drop wear is certainly recognized, but the shoulder As a result, the rubber gauge of the portion increases together with the above-mentioned flatness, so that the heat generation due to running increases due to the increase in the ground contact pressure and the heat storage property due to the increase in the rubber gauge, and the high-speed durability deteriorates.

Further, the latter method of widening the width of the belt layer not only brings about an increase in cost and weight of the product but also tends to cause peeling at the belt end portion, and it is difficult to widen the belt to the extent that shoulder drop wear can be prevented. , It does not exert sufficient effect.

In addition to measures against shoulder drop wear from the structural surface of these tires, there is, for example, Japanese Patent Publication No. 45-801 as one that prevents shoulder drop wear by improving the tread pattern. This is a "2" on the circumference of a curve or a wavy line.
By arranging the wide groove of `` book '' on both sides of the crown part of the tire, and arranging the narrow groove in parallel with this groove where the groove side surfaces contact each other at the time of grounding, it is possible to wear evenly on all tread width tread surfaces. is suggesting.

This is intended to reduce shoulder drop wear on the premise of a tire having a pattern including ribs 5, 8 having the conventional four grooves 6 shown in FIG.
-, No. 01 publication is based on the fact that the wide groove is halved from the conventional four to two, so the drainage function of the groove is substantially halved, and it is for high-speed running on a good road. Wet grip performance, which is essential for tires, is sacrificed.

Here, as one of the things to evaluate the wet grip performance, the layer of water between the road surface and the tire causes the tire to float on the water and the transmission of force between the tire and the road surface is lost. It is resistant to the hydroplaning phenomenon, which cannot be controlled by operation. Further, as a criterion for evaluating the wet grip performance, there is a skid resistance performance regarding transmission of tire driving / braking force by penetrating and draining a water film on a road surface such as a slightly wet road surface.

In order to improve such wet grip performance,
It has been said that it is preferable to form a lug or block pattern having a large drainage effect in the central region of the tread, which is the front edge of the ground contact of the tire.

However, such a pattern is apt to cause vibrations during running, and therefore, as a pattern capable of achieving smooth high-speed running, JP-A-52-111104 proposes a tire having a rib block pattern, and shoulder drop wear is also advantageous. However, it is known that abnormal wear such as so-called railway wear is occasionally seen.

[Problems to be Solved by the Invention]

Therefore, the inventors have conducted various experiments to prevent abnormal wear without deteriorating the wet grip performance, and have completed the present invention based on the following idea.

That is, in the present invention, with respect to shoulder drop wear of the tread surface, −1 change in tread rigidity reduced between the tire equator and the tread edge due to the fact that the belt layer is interrupted at the shoulder portion and the tread surface is an arc. In the rib pattern, the block pattern, and the pattern provided with siping, the tread rigidity is equalized by arranging from the tire equator side to the tread portion in the order of the simplification pattern having the smallest pattern rigidity, the block pattern, and the rib pattern. .

-The difference in tire circumference due to the tire circumference being larger than the tread line due to the tread surface being an arc is as described above. By making a block pattern with a branch groove in the central area outside the center area, the movement of the pattern at the time of grounding is made easier on the central area side, and the tread rigidity is reduced on the central area side The radial length at time is made uniform from the central region to the intermediate region. This absorbs the tire circumference difference,
Shoulder wear can be reduced. Further, by forming a rib pattern having high rigidity in the shoulder region, the radius of rotation is reduced over the entire width of the ground contact surface to absorb the difference in circumferential length.

For abnormal wear such as railway wear that tends to occur at the groove edge consisting of a wavy line or a curved line, by making the groove straight and arranging a number of sipings inclined in the tire circumferential direction in the center region Suppress.

In order to maintain the wet grip performance, two wide main grooves for main drainage that are directly passed through in the tire circumferential direction are provided to improve drainage performance. Further, by providing a sub groove for sub drainage in the crown area between the main grooves, the drainage property is improved, and a branch groove that forms a block is formed in an intermediate area between the sub groove and the main groove. As a result, the water film trampled in the tread crown region is cut and pierced by the siping in the central region and the branch groove,
Effective drainage is provided through drainage channels that are connected to each other through branch grooves.

Further, the driving / braking force, which is expected to decrease due to the straightening of the main groove and the sub groove, is compensated by arranging a large number of sipes in the central region.

It was confirmed that the tire of the present invention having these configurations can improve the above-mentioned various tire performances as compared with the conventional pattern tire.

Thus, an object of the present invention is to provide a radial tire for high-speed running on a good road, which can effectively suppress abnormal wear such as shoulder wear.

[Means for Solving the Problems]

The present invention has a circus composed of cords arranged at an angle of 80 to 90 ° with respect to the tire circumferential direction, and a belt layer composed of at least three metal cords arranged below the tire road surface adjacent to the carcass. In the tire, the tire tread surface extends in the circumferential direction and is formed by two wide linear main grooves that are symmetrical with respect to the tread center line, and a crown area (CR) between the main grooves and shoulder areas on both sides thereof ( S
H), and in the crown region (CR), two linear sub-grooves extending in the circumferential direction and symmetrical with respect to the tread center line and narrower than the main groove are provided. Due to the crown area (CR)
Is divided into a central area (CC) between the sub-grooves and an intermediate area (CM) on both sides between the sub-groove and the main groove, and further, in the central area (CC) with respect to the circumferential direction. The sipe arranged in a slanting arrangement is arranged side by side over the entire circumference, and the intermediate region (CM) is arranged side by side in the circumferential direction with an inclination with respect to the circumferential direction, and the blocks are formed by connecting the main groove and the sub groove. A block pattern provided with branch grooves to be formed, the shoulder region (SH) is a rib pattern in which ribs are continuous, and the crown region (CR) is 60% or less and 50% or more of the tread width, and The central area (CC) is 35% or less and 25% or more of the tread width, and the groove width of the main groove is 5 to 10% of the tread width (TW).
%, The groove width of the two auxiliary grooves is 0.% of the tread width (TW).
5 to 3%, the depth of the branch groove is the depth of the main groove and the sub groove connected by the branch groove, and the groove width of the branch groove is 2 to 6 mm. is there.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a meridional sectional view of a tire according to the present invention, and FIG. 3 shows a tread pattern.

A radial tire for high-speed running on a good road (hereinafter referred to as a tire) comprises a carcass 3 including plies in which cords are arranged at an angle of 80 to 90 degrees with respect to the tire circumferential direction, and a tire tread 2'adjacent to the carcass 3. And a belt layer 1 arranged below.

The carcass 3 may use a single ply made of a metal cord, or a plurality of plies made of an organic fiber cord depending on the purpose. The carcass 3 has a bead portion extending from the tread portion 2 to the side wall portion. Bead wire 4
Is wound from the inside of the tire to the outside.

In addition, another reinforcing layer (not shown) is arranged in the bead portion, particularly in the winding portion of the carcass.

The belt layer 1 uses at least three layers of plies made of metal cords, and the plies are sequentially arranged between upper and lower plies so as to form a triangle structure in which the directions of the belt cords are different from each other. The rigidity of the belt layer 1 is increased to prevent deformation of the tread portion.

In the tread portion 2, a tread rubber having a substantially constant thickness, wear resistance, and low heat generation is disposed on the belt layer 1.

Further, the tire tread 2'is provided with two main grooves 5 and 5 extending in a wide circumferential direction at symmetrical positions with respect to the tire equator, that is, the tread center line. The region CR and the shoulder region SH on both sides from the center of the main groove 5 to the tread edge are divided into three regions. The main groove 5 is formed as a linear groove whose both edges extend in a straight line in the circumferential direction.

The central region CR is set to 60% or less of the tread width TW which is the axial length of the tread edge. The name "crown area" of the tread portion itself can be easily understood by those skilled in the art, and the lower limit is the tread width T.
It is 50% or more of W.

Further, the central rib between the groove walls of the main grooves 5, 5 in the crown region CR is provided with two auxiliary grooves 6, 6 extending symmetrically with respect to the tread center line in the tire circumferential direction.

Due to the sub-grooves 6 and 6, the crown region CR is a center region C which is a range between the centers of the sub-grooves 6 and 6 in the tire axial direction.
3 in C and in the intermediate region CM between the sub-groove 6 and the center of the main groove 5
Divide. The sub-groove 6 also extends straight as a straight groove in the tire circumferential direction in order to improve drainage.

By making the main groove 5 and the sub groove 6 linear, abnormal wear such as railway wear that tends to occur at a groove edge formed of a wavy line or a bent line is suppressed.

Further, the length in the tire axial direction between the centers of the sub-grooves 6 is set to be within 35% of the tread width TW. The lower limit is about 25% of the tread width.

The main groove 5 has a groove width of 5 to 10 of the tread width TW.
%, And the groove width of the sub groove 6 is 0.5 to 3% of the tread width TW, which is narrower than the main groove 5. The depth hs of the main groove 5 and the depth hc of the sub groove 6 are set to be equal in this example.
The depths hs and hc are set according to the tire size and application.

In the center rib sandwiched by the sub-grooves 6 and 6 in the central region CC, a siping 8 that is inclined at a relatively large angle with respect to the tire circumferential direction and has both ends open in the sub-grooves 6 and 6 is provided on the entire circumference of the tire. A large number are arranged side by side. This siping 8 is
The purpose is to reduce the rigidity of the central region CC and to cut the water film when the tire rolls.

The depth he of the siping 8 is the crown region CR,
It is determined so as to equalize the rigidity with the shoulder region CH.

Further, in the intermediate rib of the intermediate region CM between the sub-groove 6 and the main groove 5, a branch groove 7 that opens at the sub-groove 6 and the main groove 5 and joins between them.
Is provided. The branch groove 7 is inclined at the same angle as the siping 8 in this example, as shown in FIG.

The branch groove 7 has a groove width of 2 to 6 mm and a depth of
The depth hs of the main groove and the depth hc of the sub groove 6 are substantially the same. Further, the branch grooves 7 are arranged in parallel in the tire circumferential direction to form a block pattern in which substantially independent blocks are arranged in parallel on the intermediate rib. The branch grooves 7 are provided at equal intervals in the circumferential direction.

Further, the shoulder region SH is formed as a shoulder rib 9 between the main groove 5 and the tread edge, and in the present embodiment, the shoulder rib 9 has a siping 1 near the tread edge.
Zeros are provided at a relatively small pitch in the tire circumferential direction to prevent abnormal wear that tends to occur at the tread edge and improve ground contact.

As described above, due to the tread surface being a circular arc and the belt layer being interrupted in the shoulder area, the tire equatorial side has a large change in tread rigidity, the central area CC of the siping pattern having siping, the branch groove. By arranging the intermediate area CM of the block pattern having 6 and the shoulder area SH of the rib pattern from the tire equator side in the ascending order of pattern rigidity, the tread rigidity can be equalized and shoulder drop wear can be prevented. In addition, by using a large number of sipings 8 and branch grooves 7 in the tread center region and the middle region, it is possible to facilitate the movement of the pattern at the time of touchdown, absorb the difference in circumferential length, and approximate the circumferential speed over the entire width of the touchdown surface. This prevents shoulder wear due to the difference in tire circumference.

Further, the main groove 5 functions as two wide main drainages that directly pass straight in the tire circumferential direction, and the sub-groove 6 functions as a central sub-drainage and forms a block in the intermediate region. By connecting the auxiliary groove 6 to the main groove by the branch groove 7, the water film trampled by the tread central region CM which is the grounding front edge portion is pierced by the siping 8 and the branch groove 7, and is connected to each other through the branch groove. Effective drainage through the drainage route.

In addition, the mid-range CM improves driving and braking performance,
The wind-cooling effect associated with rotation can be improved, tire heat generation can be suppressed, and high-speed durability can be improved.

Further, as shown in FIG. 4, the shoulder rib 9 may be provided with sipes 10, ..., 11 ... On the tread edge and the side edge facing the main groove 5. The sipings 10 and 11 are intended to prevent abnormal wear that tends to occur at the edge of the shoulder rib 9 and to improve the ground contact. This siping 1
The pitch p of 0 and 11 in the circumferential direction is an equal pitch of 3 to 20 mm.

The length of the siping in the tire axial direction is 1/8 to 1/2 of the width Ls of the shoulder rib 9, and the depth d is 3 of the depth hs of the main groove.
/ 5 to 6/5, and the width is 2 mm or less, which is specifically determined according to the tire specification size.

As described above, the tire of the present invention is provided with the above-described novel structure, so that even under severe service conditions in which a good road is operated for a long time under high speed and high load, driving / braking performance, wet road surface are obtained. Abnormal wear such as shoulder drop wear and railway wear can be effectively prevented without impairing wet grip performance such as hydroplaning performance and skid resistance performance, and tire rehabilitation can be facilitated and tire economy can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a radial tire for high-speed running on a good road, FIG. 2 is a plan view illustrating a conventional tire having a 5-rib pattern, and FIGS. 3 and 4 show an embodiment of the present invention. FIG. 5 is a plan view showing a tire pattern, and FIG. 5 is a sectional view thereof. DESCRIPTION OF SYMBOLS 1 ... Belt layer, 2 ... Tread part, 2 '... Tread tread, 3 ... Carcass, 4 ... Bead wire, 5 ... Main groove, 6 ... Sub groove, 7 ... Branch groove, 8 ... Siping, 10 ... Siping

Claims (1)

[Claims] 1. A carcass composed of cords arranged at an angle of 80 to 90 ° with respect to a tire circumferential direction, and a belt layer composed of at least three metal cords arranged below the tire tread surface adjacent to the carcass. In a tire having, a crown region (CR) between the main grooves by the two wide linear main grooves extending in the circumferential direction and symmetrical with respect to the tread center line, and shoulders on both sides thereof. It is divided into three areas (SH), and in the crown area (CR), two linear sub-grooves extending in the circumferential direction and symmetrical with respect to the tread center line and narrower than the main groove are formed. By providing the crown area (CR)
Is divided into a central area (CC) between the sub-grooves and an intermediate area (CM) on both sides between the sub-groove and the main groove, and further, in the central area (CC) with respect to the circumferential direction. The sipe arranged in a slanting arrangement is arranged side by side over the entire circumference, and the intermediate region (CM) is arranged side by side in the circumferential direction with an inclination with respect to the circumferential direction, and the blocks are formed by connecting the main groove and the sub groove. A block pattern provided with branch grooves to be formed, the shoulder region (SH) is a rib pattern in which ribs are continuous, and the crown region (CR) is 60% or less and 50% or more of the tread width, and The central area (CC) is 35% or less and 25% or more of the tread width, and the groove width of the main groove is 5 to 10% of the tread width (TW).
%, The groove width of the two auxiliary grooves is 0.% of the tread width (TW).
Radial tire for heavy load on a good road at high speed, characterized in that the depth of the branch groove is 5 to 3%, the depth of the main groove and the sub groove connected by the branch groove is the depth, and the groove width of the branch groove is 2 to 6 mm.