JP2009056955A - Pneumatic tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sufficient eccentric-wear resistant property irrespective of whether a recessed groove formed at an buttress part is located at a front part or a rear part so as to be opened on the external peripheral surface of a tread due to the wear of the external peripheral surface of the tread. <P>SOLUTION: Among a plurality of main grooves formed on the outer peripheral surface of the tread 14, the bottom surface 20a of an outer main groove 20 positioned at the outermost side in a tire width direction and dividing an inner side in the tire width direction of a shoulder land 22 is positioned at an inner side in a tire radial direction more than an outer end 23a in the tire radial direction of the recessed groove 23. A recess amount A directed to the inner side in the tire width direction of the recessed groove 23 is 4% to 8% of a size B in the tire width direction of the shoulder land 22, and in a vertical cross section along the tire width direction of the pneumatic tire 10 for a heavy load, an angle θ formed by a tangent L contacting with an outer end in the tire radial direction of the recessed groove 23 and the outer surface of the buttress part 16 at an inner side in the tire radial direction is 35° to 50°. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heavy duty pneumatic tire.

In this type of heavy-duty pneumatic tire, a plurality of main grooves extending in the tire circumferential direction are formed on the outer circumferential surface of the tread portion at intervals in the tire width direction, and a plurality of land portions are defined by these main grooves. In addition, a buttress portion extending from the outer end in the tire width direction of the tread portion toward the inner side in the tire radial direction is provided.
And conventionally, for example, as shown in Patent Document 1 below, by forming a concave groove extending along the tire circumferential direction in the buttress portion, a tread among a plurality of land portions when the heavy-duty pneumatic tire is brought into contact with the ground. The contact pressure acting on the outer end of the shoulder land portion in the tire width direction of the shoulder land portion located at both ends of the tire width direction of the tire portion is reduced. By reducing the directed shear force, the shoulder land portion of the plurality of land portions is prevented from being more easily worn than the other land portions, that is, the occurrence of uneven wear is suppressed.
Japanese Patent Laid-Open No. 11-151909

However, in the conventional heavy-duty pneumatic tire, when the outer peripheral surface of the tread portion is worn out in the process of use and the concave groove opens on the outer peripheral surface of the tread portion, the rigidity of the shoulder land portion in the tire width direction is increased. There is a problem in that uneven wear resistance is greatly reduced due to a rapid decrease in the wear resistance.
As a means for solving this problem, the outer end in the tire radial direction of the concave groove is located on the outermost side in the tire width direction among the plurality of main grooves, and more than the bottom surface of the outer main groove defining the shoulder land portion. By positioning the inner side in the tire radial direction, even if the outer peripheral surface of the tread portion is worn, it is conceivable that the groove is difficult to open on the outer peripheral surface of the tread portion.
However, in this case, it becomes difficult to suppress the occurrence of uneven wear by reducing the contact pressure due to the concave groove as described above.

  The present invention has been made in consideration of such circumstances, and has good bias resistance regardless of whether the groove formed in the buttress portion is opened on the outer peripheral surface due to wear of the outer peripheral surface of the tread portion. An object of the present invention is to provide a heavy duty pneumatic tire that can be provided with wear.

In order to solve the above problems and achieve such an object, in the heavy duty pneumatic tire of the present invention, the main groove extending along the tire circumferential direction is spaced apart in the tire width direction on the outer circumferential surface of the tread portion. A plurality of land portions are defined by these main grooves, and a buttress portion extending from the outer end in the tire width direction of the tread portion toward the inner side in the tire radial direction is provided. A heavy-duty pneumatic tire formed with a concave groove extending along a tire circumferential direction, wherein the tire is located at the outermost side in the tire width direction among the plurality of main grooves and is a tread portion of the plurality of land portions. The bottom surface of the outer main groove defining the tire width direction inner side portion of the shoulder land portion located at both ends in the width direction is located on the inner side in the tire radial direction from the outer end in the tire radial direction of the concave groove, and the concave groove Tires The amount of recess toward the inside in the direction is 4% or more and 8% or less of the size of the shoulder land portion in the tire width direction, and in the longitudinal section along the tire width direction of the heavy duty pneumatic tire, The angle between the tangent line in contact with the outer end portion in the tire radial direction of the concave groove and the outer surface of the buttress portion on the inner side in the tire radial direction is from 35 ° to 50 °.
According to the present invention, the bottom surface of the outer main groove is positioned inward in the tire radial direction from the outer end in the tire radial direction of the concave groove, and the amount of dent toward the inner side in the tire width direction of the concave groove is the shoulder. Since the land portion is 4% or more and 8% or less of the size in the tire width direction, and the angle is 35 ° or more and 50 ° or less, the outer surface of the tread portion is recessed on the outer surface due to wear. Before the groove opens, it is possible to reliably reduce the contact pressure acting on the outer end in the tire width direction of the shoulder land portion when the pneumatic tire for heavy load contacts the ground, and the outer peripheral surface of the tread portion. It is possible to suppress the rigidity of the shoulder land portion in the tire width direction from being lowered when the groove is worn and a groove is opened on the outer peripheral surface.
That is, when the amount of the recess groove is smaller than 4% of the size of the shoulder land portion in the tire width direction, the aforementioned groove groove is not opened on the outer peripheral surface due to wear of the outer peripheral surface of the tread portion. If the contact pressure cannot be reduced, and if the contact pressure exceeds 8%, the groove will not be opened when the pneumatic tire is grounded before the groove is opened on the outer periphery due to wear on the outer periphery of the tread. May be crushed by the weight of the vehicle body and the tire radial end portions may be in contact with each other, so that the above-mentioned contact pressure may not be reduced.In addition, wear on the outer peripheral surface of the tread portion may cause a groove on the outer peripheral surface. When opening, the rigidity of the shoulder land portion in the tire width direction is rapidly reduced.
Furthermore, when the amount of the concave groove is 15% or more and 30% or less of the opening width in the buttress portion of the concave groove, the above-described effects can be achieved more reliably.
Furthermore, if the angle is smaller than 35 °, the contact pressure cannot be reduced before the groove is opened on the outer peripheral surface due to wear of the outer peripheral surface of the tread portion, and the angle is reduced. When the angle exceeds 50 °, before the groove is opened on the outer peripheral surface due to wear of the outer peripheral surface of the tread portion, the groove is crushed by the weight of the vehicle body at the time of contact with the pneumatic tire and both ends in the tire radial direction The above-mentioned contact pressure may not be able to be reduced due to the contact of the parts with each other, and when a groove is opened on the outer peripheral surface due to wear of the outer peripheral surface of the tread part, the tire width direction of the shoulder land portion The rigidity at will drop rapidly.

Here, the sectional view shape along the tire width direction of the concave groove may be a single arc.
In this case, when the heavy load pneumatic tire is in contact with the ground, even if the groove is deformed so as to narrow its width, it is possible to suppress the occurrence of a location where stress is concentrated on the surface of the groove, It can suppress that it becomes easy to produce a crack in a ditch | groove.

The size of the shoulder land portion in the tire width direction may be 16% or more and 20% or less of the size of the tread portion in the tire width direction.
In this case, it is possible to reliably suppress the occurrence of uneven wear in the plurality of land portions partitioned on the outer peripheral surface of the tread portion. That is, when the size of the shoulder land portion in the tire width direction is smaller than 16% of the size of the tread portion in the tire width direction, the rigidity of the shoulder land portion in the tire width direction becomes small, and the plurality of land portions If the shoulder land portion is likely to wear limitedly, and the size of the shoulder land portion in the tire width direction is greater than 20% of the size of the tread portion in the tire width direction, The rigidity in the tire width direction of the portion increases, and the land portion located on the inner side in the tire width direction from the shoulder land portion among the plurality of land portions may be likely to be limitedly worn.

Furthermore, the depth of the outer main groove may be 28% or more and 40% or less of the size of the shoulder land portion in the tire width direction.
Further, the distance in the tire radial direction between the outer end in the tire radial direction of the concave groove and the outer end in the tire width direction of the tread portion may be 50% or more and less than 100% of the depth of the outer main groove.
Furthermore, the opening width in the buttress portion of the concave groove is 4% or more of the distance (cross-sectional height) in the tire radial direction between the inner peripheral surface of the bead portion and the portion located on the tire equator portion on the outer peripheral surface of the tread portion. It may be 7% or less.

  According to the present invention, good uneven wear resistance can be provided regardless of before or after the concave groove formed in the buttress portion opens on the outer peripheral surface due to wear of the outer peripheral surface of the tread portion.

  Hereinafter, an embodiment of a heavy duty pneumatic tire according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal sectional view along the tire width direction of a heavy-duty pneumatic tire 10. The belt layer 13 and the tread portion 14 are provided in this order. In the illustrated example, the belt layer 13 has a plurality of layers.

Furthermore, in this embodiment, the buttress part 16 extended toward the tire radial direction inner side from the tire width direction outer end 14a, 14a of the tread part 14, the bead part 17 in which the bead 11 is embedded, and the buttress part 16 Sidewall portions 18 that connect the bead portions 17 are provided.
Here, a plurality (four in the illustrated example) of main grooves 19 and 20 extending continuously along the tire circumferential direction are formed on the outer circumferential surface of the tread portion 14 at intervals in the tire width direction. A plurality of land portions 21 and 22 are defined on the outer peripheral surface of the tread portion 14 by the main grooves 19 and 20. Hereinafter, of these land portions 21 and 22, the land portions 22 positioned at both ends of the tread portion 14 in the tire width direction are referred to as shoulder land portions 22.
An outer end in the tire width direction of the shoulder land portion 22 coincides with an outer end 14a in the tire width direction of the tread portion 14, and the buttress portion 16 in the longitudinal sectional view of the heavy load pneumatic tire 10. Is connected to the outer end in the tire radial direction. Further, a concave groove 23 extending along the tire circumferential direction is formed in the buttress portion 16.

In the present embodiment, the bottom surface 20a of the outer main groove 20 that is located on the outermost side in the tire width direction among the plurality of main grooves 19 and 20 and defines the inner portion in the tire width direction of the shoulder land portion 22 is a concave groove. It is located inward in the tire radial direction from the tire radial direction outer end 23a. Further, the amount of dent A toward the inner side in the tire width direction of the groove 23 is 4% or more and 8% or less of the size B of the shoulder land portion 22 in the tire width direction. Further, in the longitudinal section along the tire width direction of the heavy duty pneumatic tire 10, a tangent line L in contact with the outer end portion in the tire radial direction of the groove 23 is on the outer surface of the buttress portion 16 on the inner side in the tire radial direction. The formed angle θ is 35 ° or more and 50 ° or less.
In the present embodiment, the tangent L is in contact with a position 1 mm away from the tire radial direction outer end 23 a in the tire radial direction on the surface of the concave groove 23. Moreover, the longitudinal cross-sectional view shape along the tire width direction of the ditch | groove 23 is a single circular arc.

Further, in the present embodiment, the size B of the shoulder land portion 22 in the tire width direction is 16% or more and 20% or less of the size C of the tread portion 14 in the tire width direction.
Further, the depth D of the outer main groove 20, that is, the amount of depression toward the inside in the tire radial direction, is 28% or more and 40% or less of the size B of the shoulder land portion 22 in the tire width direction.
Further, the distance E in the tire radial direction between the tire radial direction outer end 23a of the concave groove 23 and the tire width direction outer end 14a of the tread portion 14 is 50% or more and less than 100% of the depth D of the outer main groove 20. It has become.
The opening width F in the buttress portion 16 of the concave groove 23 is the distance in the tire radial direction between the inner peripheral surface of the bead portion 17 and the portion located on the tire equator portion on the outer peripheral surface of the tread portion 14 (cross-sectional height). 4% to 7%.

  As described above, according to the heavy-duty pneumatic tire 10 according to the present embodiment, the bottom surface 20a of the outer main groove 20 is positioned more inward in the tire radial direction than the tire radial outer end 23a of the concave groove 23. In addition, the recess amount A of the groove 23 is 4% or more and 8% or less of the size B of the shoulder land portion 22 in the tire width direction, and the angle θ is 35 ° or more and 50 ° or less. Before the concave groove 23 is opened on the outer peripheral surface due to wear of the outer peripheral surface of the tread portion 14, the contact pressure acting on the outer end in the tire width direction of the shoulder land portion 22 when the heavy load pneumatic tire 10 contacts the ground. The groove 23 can be reliably reduced and the rigidity of the shoulder land portion 22 in the tire width direction when the outer circumferential surface of the tread portion 14 is worn and the groove 23 is opened on the outer circumferential surface. It is possible to suppress a decrease.

  Further, in the present embodiment, since the longitudinal sectional shape of the concave groove 23 along the tire width direction is a single arc, the concave groove 23 narrows the width when the heavy load pneumatic tire 10 is grounded. Even if it deform | transforms in this way, it becomes possible to suppress that the location where stress concentrates on the surface of this concave groove 23, and it becomes possible to suppress that it becomes easy to produce a crack in the concave groove 23. FIG.

  Furthermore, in the present embodiment, the size B of the shoulder land portion 22 in the tire width direction is 16% or more and 20% or less of the size C of the tread portion 14 in the tire width direction. It is possible to reliably suppress the occurrence of uneven wear in the plurality of land portions 21 and 22 partitioned on the surface.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the configuration in which the shape of the longitudinal sectional view is a single circular arc is shown as the concave groove 23. However, the concave groove may be defined by two or more planes or curved surfaces. Alternatively, the concave groove may be defined by combining a flat surface and a curved surface. Further, the concave groove 23 may be formed in the buttress portion 16 so as to continuously extend over the entire circumference in the tire circumferential direction, or may be formed intermittently over the entire circumference in the tire circumferential direction.

Next, the verification test about the effect demonstrated above was implemented. In this test, nine types of heavy-duty pneumatic tires of Examples 1 to 4, Comparative Examples 1 to 4 and the conventional example were employed.
First, common points of the respective configurations of these heavy duty pneumatic tires will be described.
By forming four main grooves at intervals in the tire width direction at positions excluding the tire equator portion on the outer peripheral surface of the tread portion, the outer peripheral surface of this tread portion is positioned on the tire equator portion. And a shoulder land portion located at both ends in the tire width direction and an intermediate land portion located between the shoulder land portion and the center land portion. The size of the intermediate land portion in the tire width direction is 1.05 times the size of the center land portion in the tire width direction, and the size of the shoulder land portion in the tire width direction is the size of the center land portion in the tire width direction. 1.36 times that. The sizes of the heavy duty pneumatic tires were all 295 / 80R22.5.

In each of the heavy-duty pneumatic tires of Examples 1 to 4 and Comparative Examples 1 to 4, a concave groove extending along the tire circumferential direction is formed in the buttress portion, and the concave groove is directed inward in the tire width direction. In the longitudinal section along the tire width direction of the heavy-duty pneumatic tire, the angle between the tangent line that contacts the outer end in the tire radial direction of the groove and the outer surface of the buttress portion on the inner side in the tire radial direction Only the two places were different, and the others were all the same.
Further, in the heavy duty pneumatic tire of the conventional example, no concave groove is formed in the buttress portion.

All the 9 types of tires mentioned above are mounted on the vehicle separately, and each tire is subjected to internal pressure of 850 kPa and traveled for about 50000 km, and then the difference in the amount of wear at both ends of the shoulder land in the tire width direction is measured. Thus, the uneven wear resistance was evaluated. This evaluation was performed using an index with the measurement result obtained from the conventional heavy-duty pneumatic tire as 100.
Further, in each of the heavy duty pneumatic tires of Examples 1 to 4 and Comparative Examples 1 to 4, after the concave groove formed in the buttress portion was opened on the outer peripheral surface of the tread portion by the wear, 1 mm wear was further caused. The finite element method is used to numerically analyze the rigidity in the tire width direction of the shoulder land when traveling and the rigidity in the tire width direction of the shoulder land before the outer circumferential surface of the tread wears. The reduction rate of rigidity was calculated.
Table 1 shows the above results.

As a result, as shown in Table 1, in Examples 1 to 4, the uneven wear resistance before the concave groove formed in the buttress portion opens on the outer peripheral surface due to wear of the outer peripheral surface of the tread portion is as follows. It is possible to improve the conventional heavy load pneumatic tire, and when the groove is opened on the outer peripheral surface due to wear on the outer peripheral surface of the tread portion, the rigidity of the shoulder land portion in the tire width direction is improved. It has been confirmed that it is possible to suppress the decrease in the pressure compared to the heavy duty pneumatic tire of the comparative example.
As described above, the heavy duty pneumatic tire of the example has good uneven wear resistance regardless of before and after the concave groove formed in the buttress portion opens on the outer peripheral surface due to wear on the outer peripheral surface of the tread portion. It was confirmed that it can be made.

  Regardless of whether the groove formed in the buttress portion opens on the outer peripheral surface due to wear on the outer peripheral surface of the tread portion, good uneven wear resistance can be provided.

It is a longitudinal cross-sectional view which follows the tire width direction of the pneumatic tire for heavy loads shown as one Embodiment which concerns on this invention. FIG. 2 is a partially enlarged view of the heavy duty pneumatic tire shown in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Heavy load pneumatic tire 14 Tread part 14a Tire width direction outer end 16 Buttress part 19, 20 Main groove 20 Outer main groove 20a Bottom face 21, 22 Land part 22 Shoulder land part 23 Concave groove 23a Tire radial direction outer end A The amount of dent in the groove width inward in the tire width direction B Size of the shoulder land portion in the tire width direction L Tangent angle θ

Claims (2)

On the outer peripheral surface of the tread portion, a plurality of main grooves extending along the tire circumferential direction are formed at intervals in the tire width direction, and a plurality of land portions are partitioned by these main grooves,
This is a heavy duty pneumatic tire provided with a buttress portion extending from the outer end in the tire width direction of the tread portion toward the inner side in the tire radial direction, and having a concave groove extending along the tire circumferential direction in the buttress portion. And
Outer main groove that divides the inner portion in the tire width direction of the shoulder land portion that is located on the outermost side in the tire width direction among the plurality of main grooves and that is located at both ends of the tread portion in the tire width direction among the plurality of land portions. The bottom surface of is located in the tire radial direction inner side than the tire radial direction outer end of the groove,
The amount of dents toward the inside in the tire width direction of the groove is 4% or more and 8% or less of the size of the shoulder land portion in the tire width direction,
In a longitudinal section along the tire width direction of the heavy-duty pneumatic tire, an angle formed by a tangent line contacting the outer end portion in the tire radial direction of the concave groove with an outer surface of the buttress portion on the inner side in the tire radial direction is 35. A heavy-duty pneumatic tire characterized by an angle of not less than 50 ° and not more than 50 °. The heavy duty pneumatic tire according to claim 1,
A heavy duty pneumatic tire characterized in that a longitudinal sectional view of the concave groove along the tire width direction is a single arc.

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