JP5980562B2 - Pneumatic tire - Google Patents

Description

  The present invention includes a shoulder land portion extending in the tire circumferential direction on the tread surface, and extending in the tire circumferential direction on the inner side in the tire width direction from the ground contact end of the shoulder land portion, and the shoulder land portion is a main body land portion on the inner side in the tire width direction. And a narrow groove that is divided into a sacrificial land portion on the outer side in the tire width direction.

  In a running pneumatic tire, generally, the contact pressure tends to be higher near the ground contact edge of the shoulder land portion of the tread surface, and as a result, the ground contact end of the shoulder land portion compared to other land portions of the tread surface. The amount of wear in the vicinity increases, and uneven wear may become a problem. As a method for preventing such uneven wear, it is widely practiced to provide a narrow groove extending in the tire circumferential direction on the inner side in the tire width direction from the ground contact end in the vicinity of the ground contact end of the shoulder land portion of the tread surface. .

  The sacrificial land portion on the outer side in the tire width direction divided by the narrow groove is more effective in reducing uneven wear because the higher the rigidity, the lower the pressure and friction energy in the vicinity of the ground contact edge of the shoulder land portion. On the other hand, if the rigidity of the sacrificial land portion is made too high, stress is concentrated on the groove bottom of the narrow groove due to the deformation that the sacrificial land portion undergoes during traveling, and due to the occurrence of cracks at the groove bottom of the narrow groove, Despite the initial to mid-term use of the tire, there were problems such as loss of the sacrificial land.

  In Patent Document 1 below, a crack-resistant layer made of a crack-resistant rubber material having excellent crack resistance is used for the purpose of suppressing the occurrence of cracks at the bottom of the narrow groove and preventing the loss of the sacrificial land portion. A pneumatic tire is described in which a groove bottom surface and a groove wall surface on the outer side in the tire axial direction are formed. However, although the pneumatic tire of Patent Document 1 can suppress the occurrence of cracks and prevent the loss of the sacrificial land portion, the crack-resistant layer is formed of a rubber material, so that the effect of increasing the rigidity of the sacrificial land portion is achieved. Is difficult to obtain, and the effect of reducing uneven wear is not sufficient. In addition, since the crack-resistant layer is formed of a rubber material, if the rigidity of the sacrificial land portion is too high, there is a possibility that the generation of cracks at the groove bottom cannot be prevented.

  Patent Document 2 described below describes a pneumatic tire in which a cord extending in the tire circumferential direction is embedded in the groove bottom portion of the main groove and the movement of the groove bottom portion is restricted to improve the rigidity of the tread portion. However, even if a cord extending in the tire circumferential direction is embedded in the groove bottom portion of the narrow groove, there is no effect in suppressing the occurrence of cracks at the groove bottom due to deformation in the tire width direction received by the sacrificial land portion.

International Publication No. 2003/033280 JP 2011-37415 A

  This invention is made | formed in view of the said situation, The objective is to provide the pneumatic tire which improved the uneven wear-proof performance, maintaining the durability of a shoulder land part.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention includes a shoulder land portion extending in the tire circumferential direction on the tread surface, and extending in the tire circumferential direction on the inner side in the tire width direction from the ground contact end of the shoulder land portion. In the pneumatic tire having a narrow groove that divides the main body land portion in the tire width direction and the sacrificial land portion in the tire width direction outer side, a reinforcing layer formed by arranging reinforcing cords extending along the tire radial direction Embedded along the groove bottom of the narrow groove and the groove wall on the side of the sacrificial land, the reinforcing layer extending from the vicinity of the surface of the sacrificial land to the groove bottom, The rewind end portion is located on the outer side in the tire radial direction from the groove bottom.

  In the pneumatic tire of the present invention, the reinforcing layer formed by arranging reinforcing cords extending along the tire radial direction is embedded along the groove bottom of the narrow groove and the groove wall on the sacrifice land portion side. According to this configuration, the reinforcement cord extending along the tire radial direction can increase the rigidity of the sacrificial land portion by supporting the load, so the pressure and friction energy in the vicinity of the ground contact end of the shoulder land portion can be reduced, Uneven wear resistance performance can be improved. In addition, since the reinforcing layer is embedded around the groove bottom of the narrow groove, the occurrence of cracks at the groove bottom of the narrow groove can be suppressed, and the durability of the shoulder land portion can be maintained. At this time, since the reinforcing cord extending along the tire radial direction is embedded around the groove bottom, the occurrence of cracks at the groove bottom due to deformation in the tire width direction received by the sacrificial land portion can be effectively suppressed. In the present invention, extending along the tire radial direction includes not only extending in the tire radial direction but also extending in a direction inclined with respect to the tire radial direction.

  In the pneumatic tire of the present invention, the reinforcing cord preferably extends at an angle within a range of ± 40 ° with respect to the tire radial direction. According to this configuration, since the rigidity of the sacrificial land portion in the direction of supporting the load can be appropriately increased, the uneven wear resistance can be reliably improved.

  In the pneumatic tire of the present invention, it is preferable that the rewind end portion is located within a range of 30% or less of the groove depth from the groove bottom to the outer side in the tire radial direction. Since the rewind end of the reinforcing layer is located within this range from the groove bottom, the rigidity of the sacrificial land can be increased while maintaining the rigidity of the main body land, thereby improving the uneven wear resistance performance. it can.

  In the pneumatic tire of the present invention, the thickness of the rubber interposed between the reinforcing layer and the groove bottom is preferably 3 mm or less. According to this configuration, since the reinforcing layer is embedded near the groove bottom, the groove bottom can be appropriately reinforced by the reinforcing layer, and the generation of cracks at the groove bottom of the narrow groove can be reliably suppressed.

In the pneumatic tire of the present invention, the reinforcing cord preferably has a modulus of 100 to 1000 kgf / mm ² . If the modulus of the reinforcing cord is 100 kgf / mm ² or more, the rigidity of the sacrificial land portion can be appropriately increased by the reinforcing cord. Further, if the modulus of the reinforcing cord is 1000 kgf / mm ² or less, the reinforcing cord can follow the tire deformation under load, and therefore the reinforcing cord is not peeled off from the rubber. The modulus of the present invention is a stress measured according to JIS L 1017.

An example of a sectional view in a tire meridian direction in a shoulder land portion of the pneumatic tire of the present invention Sectional drawing which shows the modification of a reinforcement layer Sectional drawing which shows the modification of a reinforcement layer Sectional drawing which shows the modification of a reinforcement layer

  Embodiments of the present invention will be described below. FIG. 1 is an example of a sectional view in a tire meridian direction in a shoulder land portion of a pneumatic tire of the present invention. In FIG. 1, RD indicates the tire radial direction, and WD indicates the tire width direction.

  As shown in FIG. 1, the pneumatic tire according to the present embodiment includes a shoulder land portion 10 extending in the tire circumferential direction on the tread surface, and a tire circumferential direction on the inner side in the tire width direction from the ground contact end LE of the shoulder land portion 10. The narrow groove 3 extends in the direction and divides the shoulder land portion 10 into a main body land portion 1 on the inner side in the tire width direction and a sacrificial land portion 2 on the outer side in the tire width direction.

  The shoulder land portion 10 is located on the outer side in the tire width direction of the main groove (not shown in FIG. 1) extending in the tire circumferential direction on the outermost side in the tire width direction of the tread surface. In the present embodiment, an example in which the shoulder land portion 10 including the main body land portion 1 and the sacrificial land portion 2 is configured as a rib type is shown. However, in the pneumatic tire in the present invention, a tread pattern such as a rib type, a block type, or a lug type can be used without any particular limitation.

  The narrow groove 3 extends in the tire circumferential direction on the inner side in the tire width direction than the ground contact end LE of the shoulder land portion 10. Here, in the present invention, in order to effectively reduce uneven wear of the pneumatic tire, it is preferable to provide the narrow groove 3 in a region within 5% of the tread contact width with respect to the contact end LE. The groove depth D of the narrow groove 3 can be appropriately changed depending on the size of the pneumatic tire, and is, for example, 10 to 18 mm. The groove depth D of the narrow groove 3 is approximately the same as the groove depth of the main groove. In the present embodiment, the narrow groove 3 is set so that the groove width in the tire width direction WD becomes substantially constant from the tread tread surface toward the groove bottom 3a. Examples of the groove width of the narrow groove 3 include 1 to 2 mm. Moreover, the width | variety of the sacrificial land part 2 in the position of the groove bottom 3a is 8-11 mm, for example.

  In the pneumatic tire of the present invention, the reinforcing layer 4 is embedded along the groove bottom 3a of the narrow groove 3 and the groove wall 3b on the sacrifice land portion side. The reinforcing layer 4 extends from the vicinity of the surface of the sacrificial land portion 2 toward the groove bottom 3a, and is rewound around the groove bottom 3a toward the main body land portion side. The rewind end portion 4a is in the tire radial direction than the groove bottom 3a. Located on the outside. More specifically, the rewind end portion 4a is located on the outer side in the tire radial direction from the deepest end of the groove bottom 3a.

  The winding end 4a is preferably located within a range A of 30% or less of the groove depth D on the outer side in the tire radial direction from the groove bottom 3a. More preferably, the range A is 20% or less of the groove depth D from the groove bottom 3a. When the rewind end 4a is located outside the range of 30% or less of the groove depth D from the groove bottom 3a outward in the tire radial direction, the rewind end 4a of the reinforcing layer 4 is separated from the groove bottom 3a and the surface of the main body land portion 1 Therefore, the rigidity of the main body land portion 1 is also increased, and the effect of increasing the rigidity of the sacrificial land portion 2 by the reinforcing layer 4 and improving the uneven wear resistance performance is reduced.

  In the present embodiment, the end face 4b of the reinforcing layer 4 on the side opposite to the winding end part 4a is exposed at the surface of the sacrificial land part 2. However, as shown in FIG. 2, the end 4 b of the reinforcing layer 4 only needs to be positioned at least near the surface of the sacrificial land 2. At this time, the end 4b of the reinforcing layer 4 is preferably located within a range B of 20% or less of the groove depth D on the inner side in the tire radial direction from the surface of the sacrificial land 2. More preferably, the range B is 15% or less of the groove depth D from the surface of the sacrificial land portion 2. When the end portion 4b of the reinforcing layer 4 is located outside the range of 20% or less of the groove depth D from the surface of the sacrificial land portion 2 to the inside in the tire radial direction, the end portion 4b is the central portion of the groove wall 3b on the sacrificial land portion side. Therefore, stress is concentrated on the end 4b and cracks are likely to be generated therefrom.

  The thickness t of the rubber interposed between the reinforcing layer 4 and the groove bottom 3a is preferably 3 mm or less, and more preferably 2 mm or less. When the thickness t becomes larger than 3 mm, that is, when the reinforcing layer 4 is buried away from the groove bottom 3a, the groove bottom 3a cannot be properly reinforced by the reinforcing layer 4, and the groove bottom 3a of the narrow groove 3 cannot be reinforced. Cracks occur.

  The reinforcing layer 4 is configured by arranging reinforcing cords extending along the tire radial direction RD. Here, extending along the tire radial direction RD includes not only extending in the tire radial direction RD but also extending in a direction inclined with respect to the tire radial direction RD. Specifically, the reinforcement cord preferably extends at an angle within a range of ± 40 ° with respect to the tire radial direction RD, and more preferably extends at an angle within a range of ± 30 °. If the reinforcement cord extends at an angle exceeding the range of ± 40 ° with respect to the tire radial direction RD, the reinforcement cord approaches the tire circumferential direction, so that the rigidity of the sacrificial land portion 2 in the direction of supporting the load cannot be sufficiently increased. The uneven wear resistance performance cannot be improved.

Examples of the material of the reinforcing cord include organic fibers such as nylon, polyester, and rayon. The reinforcing cord is preferably modulus is 100~1000kgf / mm ^2, more preferably 300~800kgf / mm ^2. If the modulus of the reinforcing cord is smaller than 100 kgf / mm ² , the rigidity of the sacrificial land portion 2 cannot be sufficiently increased by the reinforcing cord, and uneven wear resistance performance cannot be improved. On the other hand, if the modulus of the reinforcing cord is larger than 1000 kgf / mm ² , the reinforcing cord cannot follow the tire deformation under load, and the reinforcing cord is peeled off from the rubber. The modulus of the present invention is a stress measured according to JIS L 1017.

  As a method of providing the reinforcing layer 4 as in the present invention around the narrow groove 3, when the unvulcanized tire is vulcanized and molded, the surface of the unvulcanized tire is reinforced at the portion where the narrow groove 3 is formed. A method of embedding the reinforcing layer 4 around the narrow groove 3 by arranging the reinforcing cords constituting the layer 4 and forming the narrow groove 3 with a blade of a molding die can be considered.

  According to the present invention, the above-described crack prevention effect and uneven wear reduction effect can be obtained. Therefore, the present invention is particularly useful for a heavy-duty pneumatic tire having a shoulder rib in which the problem of uneven wear at the narrow groove side end of the main body land portion is significant among the shoulder land portions.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that a reinforcing layer as described above is embedded around the narrow groove, and any conventionally known material, shape, structure, manufacturing method, etc. Can be adopted.

[Other Embodiments]
(1) In the above-described embodiment, the reinforcing layer 4 is embedded so that rubber is interposed between the reinforcing layer 4 and the groove bottom 3a and the groove wall 3b of the narrow groove 3. The thin groove 3 may be exposed at one or both of the groove bottom 3a and the groove wall 3b. An example in which the reinforcing layer 4 is exposed on both the groove bottom 3a and the groove wall 3b of the narrow groove 3 is shown in FIG.

  (2) The end 4b of the reinforcing layer 4 is not limited to the position shown in FIGS. The end 4b of the reinforcing layer 4 only needs to be positioned at least near the surface of the sacrificial land portion 2, and a part of the reinforcing layer 4 is completely exposed along the surface of the sacrificial land portion 2 as shown in FIG. You may do it.

  Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described. In addition, the evaluation item in an Example etc. measured as follows.

Uneven wear resistance A test tire (295 / 75R22.5) is mounted on the front wheel of the tractor head of a long-distance transport truck, and after running on a dry road surface of 80,000 km, the width of the step worn part is measured in the tire width direction. The reciprocal was indexed. In addition, evaluation is shown by index evaluation when Comparative Example 1 is set to 100, and the larger the numerical value, the better the uneven wear resistance performance.

Durability Performance In the evaluation of the above-mentioned uneven wear resistance performance, the presence or absence of cracks was examined during or after measurement. The crack is generated near the bottom of the narrow groove or near the end of the reinforcing layer.

Example 1
As a shoulder land portion, a pneumatic tire having the configuration shown in FIG. 1 was manufactured. As the reinforcing layer, nylon cords having a modulus of 390 kgf / mm ² were arranged in the tire radial direction. The rewinding end portion of the reinforcing layer was positioned 10% of the groove depth on the outer side in the tire radial direction from the groove bottom. The groove depth of the narrow groove was 14 mm. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 2
A pneumatic tire having the same configuration as that of Example 1 was manufactured except that the winding-up end portion of the reinforcing layer was positioned 20% of the groove depth on the outer side in the tire radial direction from the groove bottom. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 3
A pneumatic tire having the same configuration as Example 1 was manufactured except that the nylon cords were arranged in a direction inclined by 20 ° with respect to the tire radial direction. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 4
A pneumatic tire having the same configuration as in Example 1 was manufactured except that the reinforcing layer was embedded as shown in FIG. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 5
A pneumatic tire having the same configuration as that of Example 1 was manufactured except that the winding-up end portion of the reinforcing layer was positioned 30% of the groove depth on the outer side in the tire radial direction from the groove bottom. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 6
A pneumatic tire having the same configuration as in Example 1 was manufactured except that the nylon cords were arranged in a direction inclined by 40 ° with respect to the tire radial direction. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Conventional Example A pneumatic tire was manufactured in which a reinforcing layer was not embedded around the narrow groove. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 1
A pneumatic tire having the same configuration as that of Example 4 was manufactured except that the reinforcing layer was made of rubber having excellent crack resistance. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 2
A pneumatic tire having the same configuration as that of Example 1 was manufactured except that the winding end of the reinforcing layer was positioned on the inner side in the tire radial direction from the groove bottom. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 3
It has the same configuration as that of Example 1 except that the end of the reinforcing layer on the side opposite to the winding end is set to a position of 5 mm (about 36% of the groove depth) on the inner side in the tire radial direction from the surface of the sacrificial land. A pneumatic tire was manufactured. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 4
A pneumatic tire having the same configuration as that of Example 1 was manufactured except that the winding-up end portion of the reinforcing layer was positioned 50% of the groove depth on the outer side in the tire radial direction from the groove bottom. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 5
A pneumatic tire having the same configuration as in Example 1 was manufactured except that the thickness of the rubber interposed between the reinforcing layer and the groove bottom was 4 mm. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 6
A pneumatic tire having the same configuration as Example 1 was manufactured except that the nylon cords were arranged in a direction inclined by 50 ° with respect to the tire radial direction. Table 1 shows the results of the above evaluation using such a pneumatic tire.

  As shown in Table 1, in the pneumatic tires according to Examples 1 to 6, it is understood that the uneven wear resistance is improved as compared with the pneumatic tire according to Comparative Example 1. Further, the pneumatic tires according to Examples 1 to 6 have no cracks. On the other hand, in the pneumatic tire according to Comparative Example 2, although uneven wear resistance performance was improved, cracks occurred at the groove bottom of the narrow groove. In the pneumatic tire according to Comparative Example 3, although uneven wear resistance was improved, cracks occurred at the end of the reinforcing layer. Moreover, in the pneumatic tire according to Comparative Example 4, the rigidity of the land portion of the main body was increased, so that the uneven wear resistance performance was hardly improved. Moreover, in the pneumatic tire which concerns on the comparative example 5, since the reinforcement layer was separated from the groove bottom, the crack generate | occur | produced in the groove bottom of the narrow groove. Further, in the pneumatic tire according to Comparative Example 6, since the reinforcing cord approaches the tire circumferential direction, the rigidity of the sacrificial land portion cannot be sufficiently increased, and the uneven wear resistance performance is hardly improved.

DESCRIPTION OF SYMBOLS 1 Main body land part 2 Sacrificial land part 3 Narrow groove 3a Groove bottom 3b Groove wall by the side of a sacrificial land part 4 Reinforcement layer 4a Rewind end part 10 Shoulder land part RD Tire radial direction WD Tire width direction LE Ground contact edge

Claims (5)

A shoulder land portion extending in the tire circumferential direction on the tread surface, and extending in the tire circumferential direction on the inner side in the tire width direction than the ground contact end of the shoulder land portion, the main body land portion and the tire on the inner side in the tire width direction. In a pneumatic tire having a narrow groove that is divided into a sacrificial land portion on the outer side in the width direction,
A reinforcing layer formed by arranging reinforcing cords extending along the tire radial direction is embedded along the groove bottom of the narrow groove and the groove wall on the sacrifice land portion side,
The reinforcing layer extends from the vicinity of the surface of the sacrificial land portion toward the groove bottom, is wound back to the main body land portion side around the groove bottom, and the rewind end portion is located on the outer side in the tire radial direction from the groove bottom. Pneumatic tire characterized by.   The pneumatic tire according to claim 1, wherein the reinforcing cord extends at an angle within a range of ± 40 ° with respect to a tire radial direction.   3. The pneumatic tire according to claim 1, wherein the rewind end portion is located within a range of 30% or less of the groove depth from the groove bottom to the outer side in the tire radial direction.   The pneumatic tire according to any one of claims 1 to 3, wherein a thickness of rubber interposed between the reinforcing layer and the groove bottom is 3 mm or less. The pneumatic tire according to claim 1, wherein the reinforcement cord has a modulus of 100 to 1000 kgf / mm ² .

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