JP2011235824A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire further improved in interlayer distortion at a belt end of a cross belt layer.SOLUTION: This pneumatic tire includes at least two belt layers, and has a cross belt layer where reinforcing wires of two of the belt layers adjacent to each other cross each other. Each of the belt layers of the cross belt layer has a change part where the orientation direction of the reinforcing wire changes in an intermediate part from a tire equator line to an end. The orientation direction of the reinforcing wire is 80-100° with respect to the tire circumferential direction from the change part to the end of the belt layer.

Description

  The present invention relates to a pneumatic tire.

For heavy vehicles such as trucks, pneumatic radial tires for heavy loads are used. Normally, this pneumatic radial tire is provided with a plurality of belt layers made of steel cords, and in each of these layers, cross-lamination is performed so that the steel cords incline in opposite directions across the tire equator line. At least one set of cross-laminated belt layers is provided.
Usually, in belt failure (separation), the end of one belt cord of this kind of crossed belt layer and the rubber peel off and cause a crack, which is connected to the crack at the other belt cord end, resulting in the circumferential direction of the tire. It is common to occur in

In order to suppress such peeling of the belt cord end, it is only necessary to alleviate the distortion that occurs in the vicinity of the end of the belt layer during load rolling. As a method for alleviating this distortion, it is known to arrange an inter-belt rubber at both ends in the width direction between the belt layers of the cross belt layer. Further, as a method of further reducing the distortion, the belt cord may be inclined more greatly with respect to the tire equator line at the belt end portion of the belt layer having the narrower belt width among the intersecting belt layers than at the belt central portion. It is known (see Patent Document 1).
The tire of Patent Document 1 is said to be able to alleviate the distortion that occurs at the belt end as compared with the conventional tire.

JP-A-9-48212

However, under severe use conditions such as a load load, the distortion at the belt end portion further increases, and hence it is required to further improve the relaxation of the distortion.
The present invention provides a pneumatic tire with further improved distortion at the belt end of the cross belt layer.

One aspect of the present invention is a pneumatic tire,
An intersecting belt layer that includes at least two belt layers and intersects the reinforcing wires of two adjacent belt layers;
Each of the belt layers of the cross belt layer has a changing portion in which the orientation direction of the reinforcing wire changes in the middle from the tire equator line to the end portion,
From the changing portion to the end of the belt layer, the orientation direction of the reinforcing wire is 80 degrees to 100 degrees with respect to the tire circumferential direction.

At that time, pneumatic tires are for heavy loads,
The distance between the belt layers of the cross belt varies in the tire width direction,
The maximum distance among the distances between the belt layers of the cross belt is preferably 2 mm to 8 mm.

It is preferable that the changing portion is provided at a position where a distance between the belt layers of the cross belt is 150% to 160% with respect to a distance between the belt layers on a tire equator line.
In the widest belt layer in the cross belt layer, the width in the tire width direction from the change portion to the end in the tire width direction is 7% to 18% of the width of the widest belt layer. Is preferred.

  The pneumatic tire of the above aspect can further improve the suppression of interlayer distortion at the belt end of the intersecting belt layer as compared with the related art.

It is a half sectional view showing a part of a tread portion of a heavy load pneumatic radial tire of one embodiment. It is a figure explaining the structure of the belt layer used for the heavy load pneumatic radial tire shown in FIG. (A) is a figure which shows distribution of the interlayer distortion which arises in a cross belt layer, (b) is a figure which shows the change of the main distortion accompanying the cord angle of a belt edge part.

Hereinafter, the pneumatic tire of the present invention will be described in detail.
FIG. 1 is a half cross-sectional view showing a right half of a heavy-duty pneumatic radial tire (hereinafter referred to as a tire) 10 of the present embodiment. The heavy-duty pneumatic radial tire refers to a tire specified in Chapter C of JATMA YEAR BOOK 2009.
The tire 10 includes a tread rubber 12, a carcass layer 14, a side rubber 16, an inner liner 18, an inter-belt rubber 20, and belt layers 1B to 4B. Although not shown in the drawings, the tire 10 has beads, bead filler rubber, and the like.
As the tread rubber 12, the side rubber 16, the inner liner 18, the belt-to-belt rubber 20, and the bead filler rubber, well-known rubber members are used, and thus the description thereof is omitted. Since the carcass layer 14 and the bead are made of a well-known steel wire, the description thereof is omitted.

FIG. 2 is a diagram illustrating the arrangement of the belt layers 1B to 4B. Each of the belt layers 1B to 4B has a steel cord having a predetermined cord angle with respect to the tire circumferential direction.
The belt layer 1B is a layer having a steel cord disposed on the outer periphery of the carcass layer 14 in the tread portion. The steel cord of the belt layer 1B is arranged so as to extend in a direction inclined with respect to the tire circumferential direction. The tire circumferential direction refers to the tire rotation direction when the tire 10 is rotated about the tire rotation axis.
The cord angle of the steel cord of the belt layer 1B with respect to the tire circumferential direction is larger than the cord angle of the belt layer 2B described later. The belt width of the belt layer 1B is smaller than the belt width of the belt layer 2B.

  The belt layers 2B and 3B are cross belt layers having steel cords and crossing steel cords between the layers. The belt layers 2B and 3B are provided on the outer periphery of the belt layer 1B. The belt layer 2B is an inner diameter side belt layer of the cross belt layer, and the belt layer 3B is an outer diameter side belt layer of the cross belt layer. The belt layer 2B is wider than the belt layer 3B. The width of the belt layer 2B is, for example, 90 to 100% of the tread width Tw. The width of the belt layer 3B is, for example, 80 to 95% of the tread width Tw.

  Here, the tread width Tw is a contact width when the tire 10 is assembled to a regular rim, filled with a regular internal pressure, and grounded to a horizontal plane under the condition that 80% of the regular load is a load. The regular rim here refers to an “applied rim” defined in JATMA, a “Design Rim” defined in TRA, or a “Measuring Rim” defined in ETRTO. The normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load means the “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

The belt layers 2B and 3B have change portions 2B _i and 3B _i in which the cord angle changes in the middle from the tire equator line CL to the end on both sides in the tire width direction. Cord angle of the belt layer 2B, a region between 2B _i sandwiching the tire equatorial line CL (hereinafter, referred to as the belt middle portion) in a 15-25 °. In the belt layer 3B, the steel cord is inclined to the opposite side of the steel cord of the belt layer 2B with respect to the tire equator line CL at the belt center portion, and is −15 to −25 °. The cord angles of the belt layer 2B and the belt layer 3B are different from each other in positive and negative at the belt center portion (different in the inclination direction with respect to the tire circumferential direction), but have the same absolute value.

The cord angles of the belt layers 2B and 3B are 80 to 100 ° with respect to the tire circumferential direction in the regions outside the both changing portions 2B _i and 3B _i (hereinafter referred to as belt edges), and of these, the tire circumferential direction Is preferably approximately 90 °. The reason for determining the cord angle in this way is to sufficiently relax the concentration of distortion at the belt edge. The strain referred to here refers to strain generated between the belt layers 2B and 3B (shear strain generated in the tire circumferential direction). By reducing the strain concentration at the belt edge, the durability of the tire can be improved as compared with the conventional case. When the cord angle at the belt edge of the belt layers 2B and 3B is less than 80 ° or more than 100 ° with respect to the tire circumferential direction, the strain concentration at the belt edge is alleviated to some extent, but the separation is suppressed. Is not relaxed.

The width of the belt edge of the belt layer 2B is 7 to 18% of the width of the belt 2B. When the width is 7% or more, the interlayer distortion at the belt edge can be sufficiently relaxed. Further, when the width is 18% or less, the weight of the belt layer 2B can be reduced, and the cost can be reduced. The width of the belt edge of the belt layer 2B is, for example, 20 to 40 mm.
The width of the belt edge of the belt layer 3B is 5 to 13% of the width of the belt width 3B, for example, 10 to 30 mm.

  The interlayer distance between the belt layer 2B and the belt layer 3B changes in the tire width direction because the inter-belt rubber 20 is disposed between the belt layers 2B and 3B. The interlayer distance here refers to the distance between the cords of the steel cord of the belt layer 2B and the steel cord of the belt layer 3B. The maximum distance between the layers is 2.3 to 8 mm. By being 2.3 mm or more, interlayer strain at the belt edge can be sufficiently relaxed, and separation can be suppressed. In addition, when the maximum distance between the layers exceeds 8 mm, large unevenness is likely to occur in the belt layer 4B, and the thickness of the tread rubber 12 provided as the outer layer of the belt layer 4B changes discontinuously, resulting in uneven wear. easy. For this reason, the maximum distance of the interlayer distance is 8 mm or less.

The change portions 2B _i and 3B _i of the belt layers 2B and 3B are provided at positions in the tire width direction where the interlayer distance between the belt layer 2B and the belt layer 3B is 150% to 160% of the interlayer distance on the tire equator line CL. It has been. In this way, the positions of the change portions 2B _i and 3B _i are determined because the circumferential tension hardly acts in the region on the outer side in the width direction where the interlayer distance is larger than this range as compared with the region of the tire equator line CL. This is because it does not contribute to the rigidity. The rigidity here refers to a force that the ring resists when one circumferential portion of the ring is displaced when the belt layers 1B to 4B are viewed as a ring.

  FIG. 3A is a diagram for explaining the distribution of shear strain in the tire circumferential direction, where the horizontal axis is the distance in the tire width direction from the tire equator line CL and the vertical axis is the shear strain in the tire circumferential direction. The distribution of the shear strain in the tire circumferential direction is a result obtained by performing processing that reproduces the internal pressure filling and load (29.40 kN) using a finite element model that faithfully reproduces the tire 10. In FIG. 3A, the distribution of shear strain in the tire circumferential direction is a distribution in the tire width direction at two positions on the tire circumference. The two locations on the tire circumference are the position on the tire circumference where the line perpendicular to the ground contact surface from the tire rotation axis intersects the ground contact surface (the position directly below the ground contact), and the position 180 degrees opposite to this position (opposite) Position). Also, the tip of the BEC shown in FIG. 3A is a tire width direction position where the interlayer distance of the belt layers 2B and 3B starts to change (a position where the interlayer distance is 150 to 160% of the interlayer distance at the tire equator line, Here, the position is 2.3 mm or more).

According to the distribution shown in FIG. 3A, the magnitude of the shear strain in the tire circumferential direction at the position immediately below the ground and at the opposite position gradually increases from the tire equator line to the BEC tip. And the difference in shear strain at the opposite position is the largest. In general, the greater the crossing angle of the belt intersecting layer, the interlaminar shear strain of the belt layer is reduced, the belt layer 2B to BEC tip, the changing unit _2B i of 3B, by providing 3B _i, the belt layer 2B, inter 3B Thus, shear strain in the tire circumferential direction can be suppressed.

  FIG. 3B is a diagram for explaining changes in the main strain when the cord angle of the belt edge of the cross belt layer is changed with the horizontal axis representing the cord angle of the belt edge and the vertical axis representing the main strain. Two types of main strains were measured: one occurring at the BEC tip and one occurring between the layers at the belt edge. The main strain change due to the belt edge cord angle is a process that reproduces the internal pressure filling and load (29.40 kN) using a finite element model that faithfully reproduces the tire 10 similar to FIG. It is the result obtained by going.

  As can be seen from the results shown in FIG. 3B, it can be seen that as the cord angle of the belt edge approaches 90 °, both the main strain at the BEC tip and the interlayer strain at the belt edge are reduced. Therefore, by providing the belt layers 2B and 3B so that the cord angle of each belt edge is 80 to 100 °, preferably approximately 90 °, these main distortions can be suppressed.

  The belt layer 4B is a layer having a steel cord and disposed on the outer periphery of the belt layer 3B. The belt layer 4B is inclined at the same cord angle in the same inclination direction as the steel cord of the belt layer 3B. The reason why the cord angle of the belt layer 4B is the same as that of the belt layer 3B is to improve productivity. The belt width of the belt layer 4B is smaller than the belt width of the belt layer 3B.

The types of steel cords of the belt layers 1B to 4B are the same.
In the tire 10 of the present embodiment, the belt layer 2B and the belt layer 3B have the same absolute value of the cord angle, but may be different from each other.

(Example)
Hereinafter, in order to investigate the effect of the tire of the present invention, tires (tire size: 295 / 80R22.5) with various specifications of the belt layer were made as prototypes, and belt durability was evaluated.
The durability of the belt was evaluated using a prototype tire (maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “Design Rim” prescribed by TRA) using an indoor drum tester. Specifically, in an environment where the ambient temperature is 30 ° C., the step of running for 24 hours at a running speed of 45 km / hr with a constant load is repeated, and the load is increased by a certain amount each time the step is repeated. The load applied when breaking by belt separation was investigated and indexed. The higher the index, the better the durability.

  First, in all of Examples 1 to 7, Comparative Examples 1 to 3, and the conventional example described below, the belt layers 1B and 4B are the same. The steel cord wire used for the belt layers 1B to 4B was of the same type.

(Examples 1 to 3, Comparative Examples 1 to 3, Conventional Example)
Examples 1 to 3 are examples in which the cord angle of the belt edge of each layer of the intersecting belt layer is within 80 to 100 ° in the configuration of the tire 10 illustrated in FIG. 1, and Comparative Examples 1 to 3 are belt layers 2B , 3B belt edge cord angle is less than 80 ° or more than 100 °. The cord angle of the belt edge of the belt layers 2B and 3B in the conventional example is 20 °.
Table 1 shows detailed specifications and evaluation results in Examples 1 to 3, Comparative Examples 1 to 3, and a conventional example. In Table 1, the cord angle and the width direction length of the belt edge are both common to the cross belt layers. However, the cord angle of the outer diameter side belt layer has the same absolute value as the cord angle of the inner diameter side belt layer, but the inclination direction is different (−18 °). In Table 1, the maximum thickness of the cross belt buffer layer indicates the maximum thickness between the belt layers of the cross belt layer, and the modulus indicates the elastic modulus of the inter-belt rubber.

(Examples 4 to 7)
Examples 4 to 7 are examples in which the maximum thickness of the cross belt buffer layer was variously changed.
Detailed specifications and evaluation results in Examples 4 to 7 are shown in Table 2. The cord angle, belt edge width direction length, and cross belt buffer layer in Table 2 are the same as those described above for Table 1.

From the evaluation results of Examples 1 to 3, Comparative Examples 1 to 3 and the conventional example shown in Table 1, excellent belt durability is achieved by setting the cord angle of the belt edge of the cross belt layer within the range of 80 to 100 °. It can be seen that
Moreover, from the evaluation results of Examples 4 to 7 shown in Table 2, it can be seen that when the maximum thickness of the cross belt buffer layer is in the range of 2.3 to 8 mm, excellent belt durability can be obtained. In addition, even when the maximum thickness of the cross belt buffer layer exceeds 8 mm as in Example 7, the belt durability is excellent, but the belt edge on the outer diameter side of the cross belt jumps to the tread layer side, so that the tire wears out. There is a possibility of exposure to the tread surface at the end. Therefore, in order to avoid this, it is preferable to make it within 8 mm.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, this invention is not limited to the said embodiment, Of course, in the range which does not deviate from the main point of this invention, you may make a various improvement and change. is there.

DESCRIPTION OF SYMBOLS 10 Heavy load pneumatic tire 12 Tread rubber 14 Carcass layer 16 Side rubber 18 Inner liner 20 Rubber between belts 1B-4B Belt layer

Claims (4)

A pneumatic tire,
An intersecting belt layer that includes at least two belt layers and intersects the reinforcing wires of two adjacent belt layers;
Each of the belt layers of the cross belt layer has a changing portion in which the orientation direction of the reinforcing wire changes in the middle from the tire equator line to the end portion,
A pneumatic tire characterized in that an orientation direction of the reinforcing wire is 80 degrees to 100 degrees with respect to a tire circumferential direction from the change portion to an end portion of the belt layer. A heavy duty pneumatic tire,
The distance between the belt layers of the cross belt varies in the tire width direction,
2. The pneumatic tire according to claim 1, wherein the maximum distance among the distances between the belt layers of the cross belt is 2.3 mm to 8 mm.   The pneumatic tire according to claim 1 or 2, wherein the changing portion is provided at a position where a distance between the belt layers of the cross belt is 150% to 160% with respect to a distance between the belt layers on a tire equator line. .   In the widest belt layer in the intersecting belt layer, the width in the tire width direction from the change portion to the end in the tire width direction is 7% to 18% of the width of the widest belt layer. The pneumatic tire according to any one of claims 1 to 3.