JP2011173564A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of preventing partial abrasion of a tire, by uniformizing grounding pressure on a tread surface. <P>SOLUTION: In this pneumatic tire, tread rubber 10 includes a cap rubber layer 12 having the tread surface X and a base rubber layer 11 inscribed in the cap rubber layer 12, and a land part 13 partitioned by a plurality of main grooves extending along the tire circumferential direction is formed on the tread surface X. The cap rubber layer 12 includes a body rubber layer 12A having the tread surface X, a fiber reinforced layer 12B embedded in the land part 13 formed in a center area and covering reinforced fiber 12F extending in the tire circumferential direction with rubber and a low hardness rubber layer 12C circumscribed on the fiber reinforced layer 12B and lower in rubber hardness than the body rubber layer 12A. The outside end in the tire radial direction of the fiber reinforced layer 12B is positioned inside in the tire radial direction of the groove bottom of a main groove, and the low hardness rubber layer 12C is not exposed to the wall surface of the main groove. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The tread rubber has a cap rubber layer including a tread surface and a base rubber layer inscribed in the cap rubber layer, and a land portion partitioned into a plurality of main grooves extending along the tire circumferential direction is formed on the tread surface. The present invention relates to a formed pneumatic tire, and more particularly to a pneumatic tire that can effectively prevent uneven wear.

  Conventionally, a pneumatic tire is known in which a tread rubber is divided into a cap rubber layer on the tread surface side and a base rubber layer on the inner peripheral side thereof. In such a pneumatic tire, when performing high speed traveling, the center region of the tread portion bulges outward in the tire radial direction, and the diameter growth of the center region tends to be larger than the shoulder region. For this reason, the contact pressure in the center region of the tread portion is increased, and there is a problem that uneven wear occurs in which wear in the center region proceeds faster than in the shoulder region.

  In the following Patent Document 1, the tread rubber has a high modulus deformation suppressing rubber layer and a main body rubber layer sandwiching the deformation suppressing rubber layer from the outer peripheral side and the inner peripheral side, and the main rubber layer is formed from the deformation suppressing rubber layer. Also described is a pneumatic tire set to a low modulus. However, in such a pneumatic tire, since the high modulus deformation suppressing rubber layer is disposed in all regions including the center region and the shoulder region of the tread portion, the contact pressure cannot be made uniform on the tread surface. Absent. In addition, since the high modulus deformation suppressing rubber layer is exposed on the wall surface of the main groove, there is a problem that cracks are likely to occur at the interface between the two rubber layers due to the difference in the modulus of rubber on the wall surface of the main groove. .

  In the following Patent Document 2, a cap including a main rubber layer on the tread surface side, and an auxiliary rubber layer that is disposed on the inner peripheral side of the main rubber layer and has higher fiber hardness than the main rubber layer by containing short fibers. A pneumatic tire having a rubber layer and having the auxiliary rubber layer embedded only in the center region of the tread portion is described. However, in such a configuration, the ground contact pressure in the center region is excessively decreased, and conversely, the ground contact pressure in the shoulder region is increased, so that the amount of wear in the shoulder region is increased. Therefore, there was room for further improvement from the viewpoint of preventing uneven wear of the tread portion.

Japanese Patent Application Laid-Open No. 2001-206012 Japanese Patent Laid-Open No. 2008-213660

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire that can equalize the contact pressure on the tread surface and prevent uneven wear of the tire.

  The above object can be achieved by the present invention as described below. That is, in the pneumatic tire according to the present invention, the tread rubber includes a cap rubber layer including a tread surface, and a base rubber layer inscribed in the cap rubber layer, and a plurality of main tires extending along the tire circumferential direction. In the pneumatic tire in which the land portion partitioned by the groove is formed on the tread surface, the cap rubber layer is embedded only in the main rubber layer including the tread surface and the land portion formed in the center region, A fiber reinforcing layer formed by covering a reinforcing fiber extending in the tire circumferential direction with rubber; a low-hardness rubber layer circumscribing the fiber reinforcing layer and having a lower rubber hardness than the main rubber layer; and the fiber reinforcing layer The outer end in the tire radial direction is located on the inner side in the tire radial direction from the groove bottom of the main groove, and the low hardness rubber layer is not exposed on the wall surface of the main groove.

  In the pneumatic tire, since the fiber reinforcement layer is embedded only in the land portion formed in the center region of the tread portion, the center region is suppressed from bulging outward in the tire radial direction as the tire travels, The diameter growth of the center region can be suppressed. However, if only the fiber reinforced layer is embedded in the land portion of the center region, the contact pressure in the center region is excessively reduced, and conversely, the contact pressure in the shoulder region is increased, which may increase the amount of wear in the shoulder region. Concerned. In addition, the contact pressure at the center portion in the land portion of the center region is excessively decreased and the contact pressure at the end portion in the width direction of the land portion is increased, so that the wear resistance in the land portion of the center region is also deteriorated. However, in the pneumatic tire, since the low-hardness rubber layer is arranged together with the fiber reinforcement layer, the low-hardness rubber layer acts like a cushion layer, and the contact pressure in the center region is appropriately increased. Thereby, the excessive swelling to the tire radial direction outer side in a center area | region can be suppressed. As a result, in the pneumatic tire, uneven wear of the tire can be prevented.

  In the pneumatic tire, the outer end in the tire radial direction of the fiber reinforcing layer is located on the inner side in the tire radial direction from the groove bottom of the main groove, and the low hardness rubber layer is not exposed on the wall surface of the main groove. That is, the wall surface of the main groove is composed only of the main body rubber, and there is no difference in rubber hardness between the rubbers forming the wall surface of the main groove. As a result, generation of cracks on the wall surface of the main groove can be prevented.

  In the pneumatic tire, the rubber hardness of the low-hardness rubber layer is preferably 5 to 30 ° lower than the rubber hardness of the main rubber layer. According to such a configuration, the contact pressure of the entire tread surface can be more effectively equalized. As a result, in the pneumatic tire, uneven wear of the tire can be particularly prevented.

  By the way, in general, among the land portions formed in the center region, there is a tendency that the diameter growth accompanying the tire traveling increases, particularly in the central portion in the width direction of the land portion. However, in the pneumatic tire, in the fiber reinforcing layer, the reinforcing fiber at the center side in the tire width direction is located on the inner side in the tire radial direction than the reinforcing fiber on the outer side in the tire width direction. The restraining force at the central portion in the width direction is increased, and the diameter growth at this portion can be effectively suppressed, which is preferable. In this way, by making a difference in the restraining force of the fiber reinforcement layer between the center portion and the outer portion in the tire width direction of the land portion, the contact pressure in the entire land portion is made uniform, and the land portion formed in the center region It is possible to effectively prevent uneven wear.

  In the pneumatic tire, it is preferable that an inner peripheral surface of the low-hardness rubber layer is formed in an arc shape that protrudes inward in the tire radial direction. According to such a configuration, the ground pressure in the entire land portion can be more effectively equalized. As a result, uneven wear in the land portion formed in the center region can be particularly effectively prevented.

A meridian cross-sectional view showing an example of the pneumatic tire of the present invention 1 is an enlarged view of the main part of FIG. The principal part enlarged view of meridian sectional drawing which shows the other example of the pneumatic tire of this invention

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a half sectional view of a tire meridian showing an example of the pneumatic tire of the present invention. FIG. 2 is an enlarged view of a main part of FIG. 1 and 2, WD indicates the tire width direction. Since the pneumatic tire of this embodiment is symmetrical with respect to the equator plane C, the left half is omitted in FIGS. 1 and 2.

  The pneumatic tire includes a pair of bead portions 1, sidewall portions 2 that extend from the bead portions 1 outward in the tire radial direction, tread portions 3 that are continuous to the tire radial direction outer ends of the sidewall portions 2, and Is provided. The carcass layer 4 is composed of at least one (two in this embodiment) carcass ply, and an inner liner layer 5 for maintaining air pressure is disposed on the inner peripheral side thereof.

  On the outer peripheral side of the tread portion 3 of the carcass layer 4, a belt layer 6 made of two belt plies laminated on the inner and outer sides is provided to reinforce it with the effect of warp. A belt reinforcing layer 7 is provided. A rim strip rubber 8 is disposed on the outside of the bead portion 1 of the carcass layer 4, and a sidewall rubber 9 is disposed on the outside of the sidewall portion 2.

  A tread rubber 10 is disposed on the outer peripheral side of the belt reinforcing layer 7. The tread rubber 10 includes a cap rubber layer 12 including a tread surface X, and a base rubber layer 11 inscribed in the cap rubber layer 12. The tread surface A is formed with land portions 13 partitioned into main grooves 21 and 22 extending in the tire circumferential direction.

  Examples of raw materials constituting the tread rubber 10 include natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), and the like. These rubbers are reinforced with a filler such as carbon black and silica, and a vulcanizing agent, a vulcanization accelerator, a plasticizer, an anti-aging agent, a silane coupling agent, and the like are appropriately blended.

  As shown in FIG. 2, the cap rubber layer 12 includes a main rubber layer 12A including a tread surface X, a fiber reinforcing layer 12B, and a low hardness rubber layer 12C. The main rubber layer 12A preferably has a rubber hardness of 45 to 70 ° by adjusting the blending amount of the filler with respect to the raw rubber.

  The fiber reinforcing layer 12B is formed by covering the reinforcing fibers 12F extending in the tire circumferential direction with rubber. In the pneumatic tire according to the present invention, since the fiber reinforcing layer 12B is embedded only in the land portion 13 formed in the center region of the tread portion, the center region bulges outward in the tire radial direction as the tire travels. Can be suppressed, and the diameter growth of the center region can be suppressed. In this embodiment, an example is shown in which a block 13 partitioned by a main groove 21 and a lateral groove (not shown) extending in the tire width direction WD is formed as the land portion 13 formed in the center region. However, in the present invention, ribs defined only by the main groove 21 may be formed as the land portion 13 formed in the center region. In the present invention, the “center region” refers to a region between two main grooves (main grooves 21 in FIG. 2) formed on the innermost side in the tire width direction with the tire equator C interposed therebetween.

  The reinforcing fiber 12F is not particularly limited, but examples thereof include nylons such as nylon 6 and nylon 66, polyesters such as polyethylene terephthalate (PET) and polyethylene-2,6-naphthalate, vinylon, rayon, and aramid fibers. . Further, in order to alleviate the excessive decrease in the contact pressure in the center region, the rubber (covering rubber) covering the reinforcing fiber 12F is 5 to 10 ° lower than the rubber hardness of the main rubber layer 12A. preferable.

  As shown in FIG. 2, the outer end in the tire radial direction of the fiber reinforcement layer 12 </ b> B is located on the inner side in the tire radial direction from the groove bottom of the main groove 21. For this reason, even if the tread rubber 10 is worn by running of the tire, the fiber reinforcing layer 12B is not exposed to the tread surface X. In order to suppress the radial growth of the center region while preventing the occurrence of cracks on the wall surface of the main groove 21, the distance between the outer end in the tire width direction of the fiber reinforcement layer 12B and the groove wall of the main groove 21 is set to 2 to 4 mm. It is preferable that In the present invention, the main rubber layer 12A may be disposed between the fiber reinforcement layer 12B and the base rubber layer 11, but the fiber reinforcement layer 12B circumscribes the base rubber layer 11 as shown in FIG. It is preferable because it improves uneven wear resistance.

  As shown in FIG. 2, in the present embodiment, in the fiber reinforcing layer 12B, the reinforcing fiber 12F on the center side in the tire width direction is located on the inner side in the tire radial direction than the reinforcing fiber 12F on the outer side in the tire width direction. In particular, in the present embodiment, the reinforcing fibers 12F are arranged in an arc shape that is convex toward the inside in the tire radial direction. According to such a configuration, the binding force at the center portion in the width direction of the land portion 13 is increased, and the diameter growth at this portion can be effectively suppressed. As a result, the contact pressure in the entire land portion 13 can be made uniform, and uneven wear in the land portion 13 formed in the center region can be effectively prevented.

  On the other hand, the low-hardness rubber layer 12C is disposed only on the land portion 13 formed in the center region of the tread portion so as to circumscribe the fiber reinforcing layer 12B. Thereby, the low hardness rubber layer 12C acts like a cushion layer, and the ground contact pressure of the entire tread surface X can be made uniform. The rubber hardness of the low hardness rubber layer 12C is preferably 5-30 ° lower than the rubber hardness of the main rubber layer 12A, and more preferably 10-20 ° lower. If the rubber hardness difference is set within such a range, the contact pressure of the entire tread surface X can be more effectively equalized. In consideration of characteristics other than uneven wear resistance, the outer end in the tire radial direction of the low-hardness rubber layer 12C is preferably within 3 mm from the groove bottom position of the main groove 21 toward the outer side in the tire radial direction.

  Further, as shown in FIG. 2, since the low hardness rubber layer 12 </ b> C is not exposed on the wall surface of the main groove 21, the generation of cracks on the wall surface of the main groove 21 can be prevented. In order to more reliably prevent the occurrence of cracks on the wall surface of the main groove 21, it is preferable to set the interval between the low hardness rubber layer 12 </ b> C and the groove wall of the main groove 21 to 2 to 4 mm.

  As shown in FIG. 2, in the present embodiment, the inner peripheral surface of the low hardness rubber layer 12 </ b> C is formed in an arc shape that protrudes inward in the tire radial direction. According to such a configuration, the ground pressure in the entire land portion 13 can be more effectively equalized. As a result, uneven wear in the land portion 13 formed in the center region can be particularly effectively prevented.

  As a manufacturing method of the tread rubber 10 shown in FIG. 2, for example, (i) coating rubber is arranged on the outer peripheral side of the base rubber layer 11 in a circular arc shape that protrudes inward in the tire radial direction, and (ii) coating rubber The reinforcing fibers 12F coated with the above are arranged in a circular arc shape projecting inward in the tire radial direction to form a fiber reinforcing layer 12B. (Iii) A low hardness rubber layer 12C is provided on the outer peripheral side of the fiber reinforcing layer 12B. A method of arranging the inner peripheral surface so as to have an arc shape convex toward the inner side in the tire radial direction can be mentioned.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except for the point relating to the tread rubber, and any conventionally known material, shape, structure, etc. can be adopted in the present invention.

[Other Embodiments]
(1) In the above-described embodiment, an example in which the inner peripheral surface of the low-hardness rubber layer 12C is formed in an arc shape that protrudes inward in the tire radial direction has been described. However, in the present invention, as shown in FIG. 3A, the inner peripheral surface of the low hardness rubber layer 12C may be formed so as to be substantially parallel to the tread surface.

  (2) In the above-described embodiment, in the fiber reinforcing layer 12B, the reinforcing fiber 12F at the center in the tire width direction is formed so as to be positioned on the inner side in the tire radial direction than the reinforcing fiber 12F on the outer side in the tire width direction. Indicated. However, in the present invention, as shown in FIG. 3B, the reinforcing fibers 12F may be formed so as to be substantially parallel to the tread surface, or as shown in FIG. The reinforcing fibers 12F may be formed so as to overlap two in the tire radial direction.

  Examples that specifically show the structure and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Tire diameter growth Tires (265 / 75R16, rim width 16 × 7.5, air pressure setting 350 kpa) are mounted on a light truck, and when they are new and after running 30000 km on a general road, the tire outer diameter at the tire equator ( mm) was measured, and tire diameter growth (mm) was calculated from (tire outer diameter after running 30000 km (mm)) − (tire outer diameter (mm) when new).

(2) Uneven wear resistance The tires (265 / 75R16, rim width 16 × 7.5, air pressure setting 350 kpa) are mounted on a light truck, and after driving 30000 km on a general road, the main groove depth of the rear wheel tire and the new tire The main groove depth of the rear wheel tire was measured in the center region and shoulder region of the tread part, respectively ((main groove depth after running 30000 km (mm))-(main groove depth when new) (mm) The amount of wear (mm) was measured. In addition, it means that it is excellent in uneven wear resistance, so that the difference in wear amount is small in the center area | region and shoulder area | region of a tread part.

Example 1
A pneumatic tire including the cap rubber layer 10 shown in FIGS. 1 and 2 was manufactured. The main groove depth when new is 12.4 mm in the center region and 10.1 mm in the shoulder region, the rubber hardness of the main rubber layer 12A is 53 °, and the rubber hardness of the covering rubber in the fiber reinforcing layer 12B is 48 °. The rubber hardness of the low hardness rubber layer 12C was set to 38 °. The results are shown in Table 1.

Comparative Example 1
Air having the same configuration as that of Example 1 except that the cap rubber layer 10 shown in FIGS. 1 and 2 is configured only by the main rubber layer 12A and is not provided with the fiber reinforcing layer 12B and the low hardness rubber layer 12C. A tire was produced. The results are shown in Table 1.

Comparative Example 2
The cap rubber layer 10 shown in FIGS. 1 and 2 is composed of the main body rubber layer 12A and the fiber reinforcing layer 12B, and has the same structure as that of the first embodiment except that the low hardness rubber layer 12C is not provided. Tires were manufactured. The results are shown in Table 1.

  From the results of Table 1, compared to the pneumatic tire of Comparative Example 1, both the tires of Comparative Example 2 and Example 1 have suppressed tire diameter growth in the center region. However, in the pneumatic tire of Comparative Example 2, it can be seen that the contact pressure in the center region is excessively decreased, and conversely, the contact pressure in the shoulder region is increased. As a result, it can be seen that the amount of wear in the shoulder region increases, and uneven wear of the tire cannot be prevented. On the other hand, in the pneumatic tire of Example 1, the contact pressure in the center region can be appropriately reduced while suppressing the increase in contact pressure in the shoulder region. As a result, it can be seen that uneven wear of the tire can be prevented.

3: Tread part 10: Tread rubber 11: Base rubber layer 12: Cap rubber layer 12A: Main body rubber layer 12B: Fiber reinforcing layer 12C: Low hardness rubber layer 12F: Reinforcing fiber 13: Land part

Claims (4)

The tread rubber has a cap rubber layer including a tread surface and a base rubber layer inscribed in the cap rubber layer, and a land portion partitioned into a plurality of main grooves extending along a tire circumferential direction is the tread surface. In the pneumatic tire formed in
The cap rubber layer includes a main body rubber layer including the tread surface, a fiber reinforcement layer formed by covering a reinforcing fiber extending in the tire circumferential direction with rubber embedded only in the land portion formed in a center region, and A low-hardness rubber layer that circumscribes the fiber reinforcement layer and has a rubber hardness lower than that of the main rubber layer,
The outer end in the tire radial direction of the fiber reinforcement layer is located on the inner side in the tire radial direction from the groove bottom of the main groove, and the low hardness rubber layer is not exposed on the wall surface of the main groove. And pneumatic tires.   The pneumatic tire according to claim 1, wherein the rubber hardness of the low-hardness rubber layer is 5 to 30 degrees lower than the rubber hardness of the main rubber layer.   The pneumatic tire according to claim 1 or 2, wherein the reinforcing fiber on the center side in the tire width direction in the fiber reinforcing layer is located on the inner side in the tire radial direction than the reinforcing fiber on the outer side in the tire width direction.   The pneumatic tire according to claim 3, wherein an inner peripheral surface of the low-hardness rubber layer is formed in an arc shape that protrudes inward in the tire radial direction.

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