JPS63247103A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve abrasion resistance and crack resistance of thin groove by specifying the belt structure at tread section and setting the shape factor of the thin groove made in shoulder section and extending in circumferential direction of tire within a predetermined range. CONSTITUTION:Four belt layers 2(2a-2d) composed of metallic cords are arranged between a carcass layer 3 and a tread 1 while a thin groove 5 is made in the shoulder section of tread in circumferential direction of tire so as to prepare a radial tire. Here, cords in second and third belt layers 2b, 2c are crossed each other with angle of 10-30 deg. against the circumferential direction of the tire. First belt layer 2a is arranged at both shoulder sections with the cord angle thereof being set in the range of 40-75 deg.. An organic fiber cord layer 10 is placed between the carcass layer 3 and the second belt layer 2b in the central area of crown. It is formed such that the shape factor (m) defined by a formula m=(d2-d1)/h is set in the range of 0.8-1.2.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to trucks, buses, etc., which have improved wandering performance, improved wear resistance, and improved crank resistance of narrow grooves in the shoulder portion. The present invention relates to a pneumatic radial tire suitable for heavy-duty vehicles.

[Prior art]

In recent years, radial tires have come to be used on heavy-duty vehicles such as trucks and lotuses, demonstrating their excellent high speed performance, wear resistance, and low fuel consumption. In radial tires for heavy-duty vehicles, the heald layer of the tread is generally made of metal cord and has extremely high rigidity in order to withstand the heavy load.

However, heavy-duty radial tires with high tread rigidity are used with additional internal pressure, so if they are driven on a road surface with ``ruts'', they will release from the road surface when escaping from the ruts. A so-called wandering phenomenon occurs in which the handle is taken off due to excessive external force.

This wandering phenomenon is largely caused by canter thrust, so one of the countermeasures is to create narrow grooves along the circumferential direction of the tire in the shoulder area of the torso surface.
This reduces the shear rigidity of the shoulder portion against lateral force.

However, according to the results of a detailed study by the inventors, when providing a narrow groove in the shoulder part as described above, if the narrow groove position is close to the shoulder end, the bottom of the narrow groove will be located along the tire circumferential direction. Another problem is that cracks are more likely to occur, and if the narrow grooves are moved closer to the center of the tread in order to reverse the occurrence of cranking, this will substantially reduce the tread width and reduce wear resistance. It turns out that there is a problem.

[Purpose of the invention]

The present invention provides a radial tire in which narrow grooves are provided in the shoulder portion for anti-wandering performance, which improves wear resistance without impairing anti-wandering performance.
The purpose of the present invention is to provide a pneumatic radial tire that can improve the crank resistance of L and narrow grooves.

[Structure of the invention]

For this reason, the present invention provides a radial tire in which at least three heald layers made of metal cords are arranged between the carcass layer and the tread, and narrow grooves extending in the tire circumferential direction are provided in the shoulder part of the I/red surface. (1) The cords of the second heald layer and the third heald layer counting from the carcass layer in the tread direction are crossed with each other at an angle of 10° to 30° with respect to the tire circumferential direction, (
2) The first heald layer is spaced apart from each other in the crown center region and is arranged in a part of both shoulderers, and furthermore, the cord angle of the first belt layer with respect to the tire circumferential direction is set to 40' to 75°, ( 3) An organic fiber cord layer with a cord angle of 0° to 10'' with respect to the tire circumferential direction is arranged between the carcass layer and the second belt layer in the central region of the crown, and the total cord of this organic fiber cord layer is The strength is set to be 24.0 kg/cm or more per unit width, and (41) the groove depth measured in the tire radial direction of the narrow groove on the tod surface is measured from the inner edge of the shoulder part side of the a opening to a part of the groove parallel to the torso surface. When the distance measured to the outer surface is d1, and the distance measured from the inner wall surface on the shoulder side of the groove bottom to the outer surface of the shoulder part parallel to the Tresoto surface is d2, d,
The gist of the present invention is a pneumatic radial tire that satisfies +<15 mm, dB<d2, and has a shape factor m defined by the following equation of 0.8 to 1.2.

d2-d,.

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is an explanatory half-sectional view in the meridian direction showing an example of the essential parts of the radial tire of the present invention. Moreover, FIG. 2 is an explanatory plan view of the tread surface.

In FIG. 1, in tire A, a belt layer 2 made of a metal cord is arranged annularly in the tire circumferential direction between a carcass layer 3 and a tread.

This heald layer 2 consists of at least three layers, counting from the carcass layer 3 to the tread 1: a first Peruvian layer 2a1, a first belt layer 2b, a third heald layer 2C1, and a third heald layer 2C1. It consists of a fourth heald layer 2d.

Note that the carcass layer 3 may have one or more layers.

In the present invention, the following requirements are defined for this tire.

(1) Second heald layer 2b and third heald layer 2
10° to the circumferential direction of the tire.
crossed each other at an angle of 30°.

(2) The first heald layer 2a is spaced apart from each other in the crown center region T, and arranged on both shoulder parts, and the cord angle of the first heald layer 2a with respect to the tire circumferential direction is set at 40° to 75°. That's what I did.

The distance W that separates the first heald layer 2a from each other in the crown central region T is 25 to 4 times the ground contact width TW of the tread surface.
The range is preferably 5%. If it is less than 25%, it is not possible to lower the radial cross-sectional bending rigidity of the crown central region T, which is susceptible to stress concentration, to provide flexibility, and to alleviate stress.On the other hand, if it exceeds 45%, This is because the reinforcing effect of the first heald layer 2a is reduced and uneven wear is likely to occur in the shoulder portion.

(3) An organic fiber cord layer 10 having a cord angle of 0° to 100 with respect to the tire circumferential direction is arranged between the carcass layer 3 and the second heald layer 2b in the crown central region T, and this organic fiber cord layer The total strength of the 10 cords shall be 240 kg/cm or more per unit width. The organic fiber cord layer 10 may have one or more layers.

As described above, by separating the first heald layers 2a from each other in the crown central region T, that is, by having a split structure, the crown central region T is particularly susceptible to stress concentration caused by unevenness such as stones and protrusions on the road surface. To improve tire durability by lowering the tire radial cross-sectional bending rigidity and dispersing the stress concentrated at the belt end, and to prevent the occurrence and growth of cranks at the bottom of the narrow groove installed in the tire shoulder. Furthermore, in order to prevent a decrease in the dimensional stability of the tread portion due to a decrease in the reinforcing function of the belt layer in the central region of the crown, which was a drawback of the conventional splint structure, the first heald layer 2a is attached to each other. The machine fiber cord layer 10 is interposed between the carcass layer 3 and the second belt layer 2b in the crown central region T, which are spaced apart to form a gap, to enhance the circumferential reinforcing effect.

The organic fiber cord layer 10 is made of a cord such as a nylon cord, a polyester cord, or an aromatic polyamide fiber cord, for example.

The cord angle of the organic fiber cord layer 10 with respect to the tire circumferential direction is preferably a low angle from the viewpoint of ensuring dimensional stability, less than 10 degrees, preferably substantially 0 degrees.

Further, the total strength of the cords of the organic fiber cord layer 10 is 240 kg/cm or more per unit width, preferably 300 kg/cm.
/cm or more. Here, the total strength refers to the product of the number of cords inserted per unit width and the cord strength, and is expressed by the following formula.

F-Σni fi F: Total strength, ni: Number of cords inserted per unit width of organic fiber cord (1/cm), fi: Breaking strength (kg) of organic fiber cord.

The fourth belt layer 2d is arranged as a protective layer if necessary, and is made of a cord such as a steel cord or an aromatic polyamide fiber cord (trade name: Kevlar). The cord angle is 10° to 30′ with respect to the tire circumferential direction.

(4) The depth of the narrow grooves 5 on the tread surface measured in the tire radial direction is h, and the distance measured from the inner edge of the groove opening on the shoulder side to the outer surface of the shoulder parallel to the tread surface is d.
I,'a When the distance measured from the inner wall surface on the shoulder side of the bottom to the outer surface of the shoulder part in parallel to the tread surface is d2, d.

<15 mm, d, < d2, and the shape factor m determined by the Kakji equation is 0.8 to 1.2.

d, -d.

In FIGS. 1 and 2, a plurality (four in this example) of main grooves 4 are provided annularly in the tire circumferential direction on the tread surface (tread surface), forming a rib pattern. In both shoulder portions of the tread 1, narrow grooves 5 are provided along the circumferential direction of the tire, and shoulder ribs 6 are formed on the outer sides of the grooves. Further, the outer surface 6f of the shoulder rib 6 has a parabolic or arcuate curved surface.

In the present invention, the width occupied by the shoulder rib 6 with respect to the ground contact width TW of the tread surface, that is, the distance d1 measured from the shoulder-side inner wall of the groove opening of the narrow groove 5 to the outer surface of the shoulder part parallel to the tread surface is 15 mm. within the range, and
And it is set to be smaller than the distance d2 (dl<d2) measured from the shoulder side inner wall of the narrow/#5 groove bottom to the outer surface of the shoulder part in parallel to the tread surface.

Moreover, from these d, d2 and the groove depth 11 of the narrow groove 5 measured in the tire radial direction, the shape factor m defined by the above formula is set to be in the range of 0.8 to 1°2. Ru.

If the distance d is made larger than 15 mm, the effective ground contact width of the tread surface becomes too narrow, resulting in poor wear resistance.If the distance d is increased further, the stiffness of the shoulder portion against lateral force is not sufficiently reduced. As a result, the wandering prevention performance also deteriorates.

Further, in the present invention, the distances d, d2 between the outer surface of the shoulder part and the groove opening and groove bottom of the narrow groove 5 are set to dl<d2 as described above, and the shape factor m
By setting the value in the range of 0.8 to 1.2, the distribution of bending stress in the shoulder rib 6 can be approximated to a "cantilever beam of equal strength" in terms of material mechanics. That is, the bending stress when a lateral force is applied to the shoulder rib 6 can be made almost uniform in the tire radial direction from the tread surface to the position corresponding to the bottom of the narrow groove 5. Therefore, this state that approximates a cantilever beam of equal strength avoids stress concentration on the groove bottom of the narrow groove 5, and prevents the generation of cracks along the tire circumferential direction at the groove bottom. become.

In order to make the shoulder rib 6 more approximate to the above-mentioned cantilever beam of equal strength, it is most preferable that the outer surface 6f of the shoulder rib 6 is formed into a parabolic curved surface. However, as long as a state similar to a cantilever beam of equal strength is obtained, the outer surface 6f may be arcuate or tapered.

When the shape factor m is smaller than 0.8, cracks are likely to occur at the bottom of the narrow groove 5 due to stress concentration, or wear resistance is deteriorated.

Moreover, when the shape factor m is larger than 1.2, the rigidity of the shoulder rib 6 becomes too large, and the wandering prevention performance deteriorates.

Further, in the present invention, the shoulder rib 6 as described above
The cross-sectional shape of the groove bottom of the narrow groove 5 forming the groove 5 is preferably rounded, such as in a U-shape, in order to avoid stress concentration. Further, the groove width of the narrow A5 is sufficient as long as it has the form of a groove, and the groove width is preferably in the range of 1 to 5 mm, and more preferably about 2 to 3 mm. Further, in order to maintain the wandering prevention performance, the groove depth h is preferably set to be approximately the same as the depth of the groove main tj, 4], and more preferably 0.7H<h<l.

It is best to keep it in the OH range. Generally, a size of around 151 is suitable.

Examples are shown below.

Examples The following tires of the present invention, comparative tires A, B, C1, and conventional tires were evaluated for durability, crank growth, and wandering performance. The results are shown in Table 2 below.

(a+ Tire of the present invention.

Tire circumferential direction 10.00 R2014PR0 Force - The waste layer is one steel cord layer. The heald part structure shown in FIG.

Organic fiber cord layer: Nylon 1890 D/2 (strength 40 kg), 8.4 pieces/cm x 1 ply (arranged in the direction crossing the second heald layer 2b), F-336
kg/cm, )Red Ground contact width 185mm 0 Mutual spacing of the first belt layer 2a 60mm+, Specifications of the heald layer are as shown in Table 1 below. The tread pattern is second
figure. d, , d, , h are shown in Table 2.

(b) Comparative tire A0 Tire size 10.0OR2014PR, carcass layer is one steel cord layer. The belt section structure shown in FIG. 1 except that the first belt layers 2a are not spaced apart from each other (ie, there is no organic fiber cord layer). The specifications of the belt layer are as shown in Table 1 below. The tread pattern is second
figure. d1, d, , h are shown in Table 2.

(C) Comparison tire B0 Tire size 10.0OR2014PR, carcass layer is one steel cord layer. The belt part structure shown in FIG. Organic fiber cord layer: Nylon 1890 D/2.8.4 wood/cmXl ply (arranged in the direction crossing the second belt layer 2b), F = 336 kg / Cff10 Tread contact width 185 mm. The mutual spacing of the first belt layer 2a is 60 mm. The specifications of the belt layer are shown in Table 1 below.

The tread pattern is shown in Figure 2.

d, , d, , h are shown in Table 2.

(dl Comparison tire C0 Tire size 10.0OR2014PR, carcass layer is one steel cord layer. Belt part structure shown in Figure 1. Organic fiber cord layer; Nylon 1890 D/2.8.4 pieces/cm x 1 ply ( (arranged in the direction crossing the second belt layer 2b), F = 336 kg / c 1110, tread contact width 185 mm, mutual spacing of the first heald layer 2a 601. The specifications of the belt layer are according to Table 1 below. Tread pattern Figure 2.

dI% d2 and h are shown in Table 2.

(e) Conventional tires.

Tire size 10.0OR2014PR0 - The waste layer is one steel cord layer. The belt portion structure shown in FIG. 1 except that the first heald layers 2a are not spaced apart from each other (ie, there is no organic fiber cord layer). The specifications of the belt layer are shown in Table 1 below. The tread pattern is second
figure. d1, d, , h are shown in Table 2.

Quantity I (Maoyuun・bud): The depth of all main grooves of the tire to be measured before and after driving an actual vehicle on a general paved road for 50,000 km.
It was measured in units of n, and the average value of the difference between the measured values before and after the test run was taken as the amount of wear. Next, the traveling distance (50,000 km) was divided by this amount of wear to calculate the distance traveled per 1 mm of wear, and this was taken as the wear resistance.

In the table, the wear resistance calculated from each tire is expressed as an index when the wear resistance of the tire of the present invention is set as 100.

La ■ (Crack/Raw 2'i): The tire to be measured was heat aged in advance in an oven at 100°C for 2 weeks and tested using an indoor rotating drum tester with a diameter of 1707 mH to obtain a tire internal pressure of 7.25 kg/cn! , load approximately 2200 kg
, speed 45 km/hr, slip angle ±2deg (
After running for 100 hours under the following conditions (cycle fluctuation), the condition of a crank that had occurred at the bottom of the narrow groove was investigated.

The occurrence of this crank was checked around the entire circumference of the narrow groove, and a cross cut was made at the point where the largest crack occurred by visual inspection.The value of the crack length was measured in mm and was used as an index of crack resistance. .

■ (Wandering life'''): The tire to be measured was mounted on an empty 1L 3910 kg vehicle (steering axle load), and the tire was run at 8° to 90 km/hr on a test course with ruts in an empty state. Ten test drivers conducted tests in which they drove straight in ruts, in and out of ruts, and intentionally hit their tires against the rut walls at speeds of Ring, bias tire level 6
The points were scored using a 10-point system, and the average value of the 10 people was expressed as the wandering prevention performance.

The above feeling score includes the frequency of wandering, the amount of wandering movement, the speed of wandering movement,
The focus of wandering, the feel of the steering wheel, and the vehicle's behavior in and out of ruts were evaluated.

From Table 2, it can be seen that the tire of the present invention has wear resistance, crank durability,
It can be seen that the wandering performance is excellent.

〔Effect of the invention〕

As explained above, according to the present invention, the heald structure in the tread portion is defined, and the distance d1d2 from the groove opening and the groove bottom of the narrow groove provided in the shoulder portion to the outer surface of the shoulder portion is set under certain conditions. By setting the shape factor m specified from these d, d2 and the groove depth h to a certain range, the wear resistance and the crank resistance of the narrow groove can be improved without impeding the wandering prevention performance. can improve sex.

[Brief explanation of drawings]

FIG. 1 is an explanatory half-sectional view in the meridian direction showing an example of the essential parts of the radial tire of the present invention, and FIG. 2 is an explanatory plan view of the tread surface thereof. A... Tire, 1... Tread, 2... Heald layer, 2a... First heald layer, 2b... Second belt layer, 2C... Third heald layer Layer, 2d...
・Fourth belt layer, 3... Carcass layer, 4...
Main groove, 5... Thin groove, 6... Shoulder rib, 10.
...Organic fiber cord layer.

Claims (1)

[Claims] A radial tire in which at least three belt layers made of metal cords are arranged between the carcass layer and the tread, and narrow grooves extending in the tire circumferential direction are provided in the shoulder portion of the tread surface. 1) The cords of the second belt layer and the third belt layer counting from the carcass layer in the tread direction are each 10° to 30° with respect to the tire circumferential direction.
(2) The first belt layer is spaced apart from each other in the crown center region and arranged on both shoulder parts, and the cord angle of the first belt layer with respect to the tire circumferential direction is 40° to 75°, (
3) The cord angle between the carcass layer and the second belt layer in the crown center region is 0 with respect to the tire circumferential direction.
An organic fiber cord layer of 10° to 10° is arranged, and the total strength of the cord of this organic fiber cord layer is 240 kg/c per unit width.
(4) The depth of the narrow groove on the tread surface measured in the tire radial direction is h, and the distance measured from the inner edge of the groove opening on the shoulder side to the outer surface of the shoulder parallel to the tread surface is d_1. , when d_2 is the distance measured from the shoulder-side inner wall surface of the groove bottom to the shoulder outer surface parallel to the tread surface, d_1<15mm, d_1<d_
2, and a shape factor m defined by the following formula m=(d_2-d_1)/h is 0.8 to 1.2.