JP5060780B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a tire having a circumferential belt layer in which a reinforcing element such as a cord or a filament extends in a direction along the equator plane of the tire as a belt.

Regarding the belt used for reinforcing the carcass of a tire, Patent Document 1 reinforces a number of cords or filaments that cross each other with the equator plane sandwiched between them at an inclination angle of 10 to 40 ° with respect to the equator plane of the tire around the carcass. Orientation along the equator of a number of corrugated or zigzag reinforced elements of at least one layer, comprising at least two layers of cross belts, and further below the cross belt, as elements A structure having a crown reinforcing layer made of a strip is disclosed.
JP-A-2-208101

  In recent years, due to demands for higher speeds and lower floors of vehicles, mounted tires are flattened, and accordingly, the amount of radial growth of the tread portion when applying standard internal pressure tends to increase further. This increase in the radial growth amount in the tread portion is a factor that causes belt end separation particularly early because it amplifies the stress concentration at the belt end portion and leads to a decrease in durability at the portion.

  That is, in a tire having a small aspect ratio, since it becomes a problem that the diameter growth amount in the vicinity of the tread portion, particularly the shoulder portion, when the internal pressure is applied, the circumferential belt layer by the reinforcing element arranged in the circumferential direction of the tire is a problem. Thus, for example, the above-described Patent Document 1 has proposed a technique for suppressing diameter growth.

  However, when the flat ratio is further reduced, specifically, when the flat ratio, which is the ratio of the cross-sectional height to the cross-sectional width of the tire, is 0.70 or less, the width of the circumferential belt layer is not further increased. As a result, it is difficult to suppress the intended diameter growth. However, increasing the width of the circumferential belt layer is a new problem that it leads to a decrease in durability. This is because one or two or more inclined belt layers in which a large number of cords extending in a direction inclined with respect to the equatorial plane of the tire are covered with rubber are arranged on the outer side in the radial direction of the circumferential belt layer. When the direction belt layer width is widened, a large circumferential shear input acts on the rubber layer between the inclined belt layer and the end of the circumferential belt layer, which causes separation between the belt layers. Because. Therefore, the width of the circumferential belt layer cannot be easily increased.

  The present invention provides a way to suppress interlayer separation with the inclined belt layer even when the circumferential belt layer width is widened, and thereby the durability of the belt in a tire having a small aspect ratio, especially a heavy duty radial tire. The purpose is to improve performance.

When the width of the circumferential belt layer is increased in order to suppress the diameter growth of the tread portion of the tire, the most serious problem is between the end of the outermost layer of the circumferential belt layer and the adjacent inclined belt layer. This is a separation that occurs in the belt, and this causes a reduction in belt durability.
This belt interlayer separation is due to the fact that there is a deformation difference between the circumferential belt layer and the inclined belt layer, so that circumferential shear strain acts on the interlayer rubber. Due to this distortion, a crack generated from the vicinity of the end of the circumferential belt layer propagates between the belt layers and reaches belt separation, so that traveling with the tire becomes impossible.

  Therefore, as a result of intensive investigations on ways to suppress such belt separation, it is very effective to reduce the concentration of strain at the end of the circumferential belt layer to suppress this belt separation. found.

That is, the gist configuration of the present invention is as follows.
(1) A carcass straddling a toroidal shape between a pair of bead portions, and a plurality of reinforcing elements extending along the equatorial plane of the tire are coated with rubber on the radially outer side of the crown portion of the carcass, at least 1 A belt formed by sequentially arranging a circumferential belt layer of layers and at least two inclined belt layers in which a plurality of cords extending in a direction inclined with respect to the equator plane O of the tire are covered with rubber, A tire in which a tread is arranged on the outer side in the radial direction of the belt,
The width of the circumferential belt layer is 60% or more of the total width of the tire and narrower than the width of the adjacent inclined belt layer, and the modulus of the covering rubber of the circumferential belt layer disposed on the outermost side is M (C) And when the modulus of the coating rubber of the inclined belt layer adjacent to the widthwise end of the circumferential belt layer is M (A),
M (C) = M (A)
Pneumatic tire characterized by satisfying

(2) When there is a cushion rubber layer between the circumferential belt layer and an inclined belt layer adjacent to the circumferential belt layer, and the modulus of the cushion rubber layer is M (B), the circumferential belt For the modulus M (C) of the coating rubber of the layer and the modulus M (A) of the coating rubber of the inclined belt layer adjacent to the widthwise end of the circumferential belt layer,
M (C) = M (A) = M (B)
The pneumatic tire according to (1) , wherein the relationship is satisfied.

( 3 ) The air according to (2) , wherein the cushion rubber layer is disposed within a range of 50 mm away from the widthwise end of the circumferential belt layer inward in the belt layer width direction. Enter tire.

( 4 ) The pneumatic tire according to (2) or (3) , wherein the cushion rubber layer has a thickness of 5 mm or less.

( 5 ) The pneumatic tire according to any one of (1) to (4) , wherein the cord of the inclined belt layer has an inclination angle of 40 ° or more with respect to an equatorial plane of the tire.

  According to the present invention, the circumferential belt layer width is increased to suppress the radial growth of the tread portion particularly in a tire having a small aspect ratio and to suppress the interlayer separation starting from the width end portion of the circumferential belt layer. be able to. Therefore, it is possible to provide a tire with a small aspect ratio that greatly improves the durability of the belt.

The tire according to the present invention will be described in detail with reference to FIG.
That is, in FIG. 1, reference numeral 1 denotes a carcass straddling a toroidal shape between a pair of bead portions (not shown), and along the equatorial plane O of the tire on the radially outer side of the crown portion of the carcass 1. At least one circumferential belt layer 2a and 2b in the illustrated example, and a plurality of cords C extending in an inclined direction with respect to the equator plane O of the tire, with a plurality of extending reinforcing elements S covered with rubber. The belt 4 is formed by sequentially laminating two inclined belt layers 3a and 3b in the illustrated example, in which at least two layers are arranged in a direction in which the cords intersect with each other. The tread 5 is arranged radially outside.

  The reinforcing element S constituting the circumferential belt layers 2a and 2b includes, in addition to cords and filaments, cords and filaments that are shaped into a corrugated shape, linear high elongation cords having initial elongation, and high elasticity. For example, an aromatic polyamide fiber which is a simple organic fiber can be used.

  Here, the widths of the circumferential belt layers 2a and 2b need to be set to 60% or more of the total width TW of the tire and narrower than the width of the adjacent inclined belt layers. First, in order to keep the tread diameter growth during application of internal pressure within a certain range, the width of the circumferential belt layer needs to be 60% or more of the total tire width TW. This is because in flat tires, the diameter growth particularly in the vicinity of the shoulder portion increases and the belt durability is deteriorated, so that it is necessary to dispose the circumferential belt layer near the shoulder portion. The upper limit is preferably 95% due to tire shape restrictions.

  Furthermore, the width of the circumferential belt layers 2a and 2b needs to be narrower than the width of the adjacent inclined belt layer 3a. This is because if the end of the adjacent inclined belt layer is located on the inner side in the width direction than the end of the circumferential belt layer, the input to the end of the inclined belt layer is increased and the durability is lowered.

  In the example shown in FIG. 1, the circumferential belt layers 2a and 2b have the same width, but they need not have the same width.

  The width of the inclined belt layer 3a, which serves as a reference for the width of the circumferential belt layer, is preferably about the same as the width of the tread in order to improve the partial wear of the tread portion. In the example shown in FIG. 1, the width of the inclined belt layer 3a is wider than the width 3b. However, when the width is the same, the belt end overlaps and an abrupt stiffness change occurs. Since there is a concern that it will worsen, the width is changed.

Further, when the width of the circumferential belt layer is widened, distortion concentrates on the end of the circumferential belt layer, resulting in separation, and it is difficult to obtain a sufficiently satisfactory tire life. Therefore, in the present invention, the modulus of the covering rubber of the circumferential belt layer disposed on the outermost side is M (C), and the modulus of the covering rubber of the inclined belt layer 3a adjacent to the widthwise end of the circumferential belt layer is M (C). A)
M (C) = M (A)
By satisfying the above, the strain concentrated on the end portion of the circumferential belt layer is alleviated.

That is, the cause of the separation is circumferential shear strain, which is caused by strain concentrated on the end rubber of the circumferential belt layer due to the circumferential deformation difference between the circumferential belt layer end and the adjacent inclined belt layer. The result is as described above. Therefore, if this strain is relaxed, the generation of crack nuclei can be suppressed.
For this purpose, the modulus M (C) of the covering rubber of the circumferential belt layer is made equal to the modulus M (A) of the covering rubber of the adjacent inclined belt layer, so that the strain is concentrated on the inclined belt layer side, It is possible to alleviate distortion at the end of the directional belt layer.

This is because the shear strain generated due to the deformation difference in the circumferential direction of the belt makes the deformation M (C) equal to the modulus M (A) , thereby concentrating the deformation on the coated rubber of the inclined belt layer. This is because the deformation of the coated rubber is relieved .

Next, the example shown in FIG. 2 shows that the cushion rubber layer 6 is further disposed between the circumferential belt layer 2b and the inclined belt layer 3a in the belt structure shown in FIG. This promotes the relaxation of distortion at the part. At that time, the modulus of the cushion rubber layer 6 is M (B), the modulus M (C) of the coating rubber of the circumferential belt layer, and the modulus of the coating rubber of the inclined belt layer adjacent to the widthwise end of the circumferential belt layer. M (A) is
M (C) = M (A) = M (B)
It is preferable that the relationship is
Because, if the modulus M (A) of the coating rubber of the inclined belt layer is extremely reduced, cracks will be generated from the inclined belt layer side, so it is necessary to further promote the relaxation of the distortion here. is there. For this purpose, it is advantageous that the modulus M (B) of the cushion rubber layer is made equal to or less than the modulus M (A) to prevent strain from concentrating on the rubber in the circumferential belt layer and further the inclined belt layer .

Here, it is as follows when the suitable range is shown about the modulus (50% modulus) of each above-mentioned belt layer.
M (A): 17.0-32.0 (MPa)
M (B): 10.0-25.0 (MPa)
M (C): 25.0-40.0 (MPa)

  Further, the cord arrangement of the inclined belt layers 3a and 3b is preferably such that the inclination angle of the tire with respect to the equator plane O is 40 ° or more. That is, if it is less than 40 °, it is difficult to ensure both shear rigidity and rigidity in the belt width direction, and there is a possibility that the wear performance and the cord breaking resistance performance when riding on the protrusions are lowered.

  In the tire structure shown in FIGS. 1 and 2, a belt structure having the specifications shown in Table 1 was applied, and tires for truck vehicles of size 435 / 45R22.5 were respectively prototyped. The obtained tire was assembled in a rim of size 14.00 x 22.5, the internal pressure was adjusted to 900 kPa, drum running under the conditions of drum load: 59.0kN and drum rotation speed: 60.0km / h, belt separation The time until the failure occurred was measured. The measurement results are also shown in Table 1 as an index when the conventional example is set to 100. The larger this number, the higher the durability.

  The rubber modulus of each belt layer is the hardness measured by a Shore A hardness meter for each rubber in each tire shown as the conventional example, the comparative example, and the invention example, and the modulus of the coating rubber of the circumferential belt layer is 100. As an index. The larger the value, the higher the modulus.

It is sectional drawing of the width direction of the tire according to this invention. It is sectional drawing of the width direction of another tire according to this invention.

Explanation of symbols

1 Carcass 2a, 2b Circumferential belt layer 3a, 3b Inclined belt layer 4 Belt 5 Tread

Claims (5)

A carcass straddling a toroidal shape between a pair of bead portions, and a plurality of reinforcing elements extending along the equatorial plane of the tire are coated with rubber on the radially outer side of the crown portion of the carcass. A belt formed by sequentially arranging a directional belt layer and at least two inclined belt layers in which a number of cords extending in a direction inclined with respect to the equator plane O of the tire are covered with rubber, A tire having a tread arranged radially outward,
The width of the circumferential belt layer is 60% or more of the total width of the tire and narrower than the width of the adjacent inclined belt layer, and the modulus of the covering rubber of the circumferential belt layer disposed on the outermost side is M (C) And when the modulus of the coating rubber of the inclined belt layer adjacent to the widthwise end of the circumferential belt layer is M (A),
M (C) = M (A)
Pneumatic tire characterized by satisfying A cushion rubber layer is provided between the circumferential belt layer and an inclined belt layer adjacent to the circumferential belt layer, and when the modulus of the cushion rubber layer is M (B), the circumferential belt layer is covered. For the modulus M (C) of the rubber and the modulus M (A) of the coated rubber of the inclined belt layer adjacent to the widthwise end of the circumferential belt layer,
M (C) = M (A) = M (B)
2. The pneumatic tire according to claim 1, wherein the following relationship is satisfied. 3. The pneumatic tire according to claim 2, wherein the cushion rubber layer is disposed within a range of 50 mm away from an inner side in the belt layer width direction from an end in a width direction of the circumferential belt layer . The pneumatic tire according to claim 2 or 3, wherein the cushion rubber layer has a thickness of 5 mm or less . The pneumatic tire according to any one of claims 1 to 4, wherein the cord of the inclined belt layer has an inclination angle of 40 ° or more with respect to the equator plane of the tire.

Images