JP2006205991A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of preventing overcure under the groove of a belt layer, and improving durability. <P>SOLUTION: Low thermal conductive rubber layers 21a, 21b having a lower thermal conductivity than a cap tread rubber layer 1a of a tread part 1 are selectively provided between the groove 7 and the belt layer 6 in the pneumatic tire wherein the belt layer 6 is embedded in the tread part 1 and the groove 7 is provided on the tread part 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire in which a belt layer is embedded in a tread portion and a groove is provided in the tread portion, and more specifically, overcuring under the groove of the belt layer is prevented and durability is improved. The present invention relates to a pneumatic tire.

  The vulcanization time of the pneumatic tire is set to a time until the vulcanization degree of the vulcanization rate controlling part reaches a sufficient level. In general, the vulcanization-controlling part is the part where the rubber gauge is thickest, for example, the central part of the block formed in the tread part. Such a vulcanization rate-limiting part has a slow temperature rise, so that it takes a long time to complete vulcanization. On the other hand, since the rubber gauge is thin at the lower part of the groove defining the block, it is heated more than necessary and becomes overcured. As a result, the belt layer has a difference in thermal history (vulcanization degree) between the portion under the groove and the portion under the block, which is one of the causes for reducing the durability of the pneumatic tire.

In addition, in a vulcanizer, it has been proposed to dispose a heat pipe for selectively transferring heat to a tire mold (see, for example, Patent Document 1). However, with the method of optimizing the temperature distribution of the vulcanizer, it is difficult to individually set the temperature for the central portion of the block that is the vulcanization-controlling portion and the lower portion of the groove that partitions the block portion.
JP 2002-67038 A

  An object of the present invention is to provide a pneumatic tire capable of preventing overcuring under a groove of a belt layer and improving durability.

  In order to achieve the above object, the pneumatic tire of the present invention is a pneumatic tire in which a belt layer is embedded in the tread portion and a groove is provided in the tread portion, and is more thermally conductive than the cap tread rubber layer of the tread portion. A low thermal conductivity rubber layer having a low rate is selectively provided between the groove and the belt layer.

  In the present invention, since the low thermal conductivity rubber layer having a lower thermal conductivity than the cap tread rubber layer of the tread portion is provided between the groove and the belt layer, the heat at the portion where the low thermal conductivity rubber layer is provided. Conduction can be suppressed compared to other parts, and overcuring under the groove of the belt layer can be prevented. This flattens the thermal history of the belt layer under the groove and the block under the block, and further improves the adhesion between the belt layer cord and rubber, improving the durability of the pneumatic tire can do.

  In the present invention, the low thermal conductive rubber layer can be disposed in a portion exposed on the surface of the groove. In this case, a low heat conductive rubber layer may be laminated at a position corresponding to the groove of the cap tread rubber layer at the time of molding the tire. The low thermal conductive rubber layer can be disposed between the cap tread rubber layer and the belt layer. In this case, at the time of molding the tire, a low heat conductive rubber layer may be laminated at a position corresponding to the groove of the under tread rubber layer, or a portion corresponding to the groove of the under tread rubber layer may be replaced with the low heat conductive rubber layer.

  The thermal conductivity of the low thermal conductivity rubber layer is preferably 40% to 95% of the thermal conductivity of the cap tread rubber layer. As a result, overcuring under the groove of the belt layer can be reliably prevented. When the thermal conductivity of the low thermal conductivity rubber layer exceeds 95% of the thermal conductivity of the cap tread rubber layer, the effect of preventing overcuring under the groove of the belt layer becomes insufficient, and 40% Have difficulty. The thermal conductivity in the present invention is a thermal conductivity [W / (m · K)] measured at 25 ° C., for example, measured using a Shotherm QTM rapid thermal conductivity meter (manufactured by Showa Denko KK). It is what is done.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3 and 3, and an end portion of the carcass layer 4 is folded around the bead core 5 from the inside to the outside of the tire. On the outer peripheral side of the carcass layer 4 in the tread portion 1, a plurality of belt layers 6 are embedded over the entire circumference of the tire. These belt layers 6 include reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged such that the reinforcing cords cross each other between the layers. The tread portion 1 is formed with a plurality of main grooves 7 extending in the tire circumferential direction and a plurality of lateral grooves (not shown) extending in the tire width direction, and a number of blocks are partitioned by these grooves. On the other hand, reinforcement layers 9 to 11 including a reinforcement cord such as a steel cord are embedded in the bead portion 3.

  In the pneumatic tire, the tread portion 1 has a structure in which a cap tread rubber layer 1a and an under tread rubber layer 1b are laminated. And between the main groove 7 and the belt layer 6, low thermal conductive rubber layers 21a and 21b having lower thermal conductivity than the cap tread rubber layer 1a of the tread portion 1 are provided.

  The low thermal conductive rubber layer 21 a is disposed in a portion exposed on the surface of the main groove 7. On the other hand, the low thermal conductive rubber layer 21 b is disposed between the cap tread rubber layer 1 a and the belt layer 6. Here, both the low thermal conductive rubber layers 21 a and 21 b are provided, but it is sufficient that at least one of the low thermal conductive rubber layers 21 a and 21 b is interposed between the main groove 7 and the belt layer 6. .

  The thermal conductivity of the low thermal conductive rubber layers 21a and 21b is appropriately set based on, for example, the blending amount of silica or carbon black blended in the compound. That is, increasing the blending amount of silica decreases the thermal conductivity, and increasing the blending amount of carbon black increases the thermal conductivity. The thermal conductivity of the low thermal conductive rubber layers 21a and 21b may be set to 40% to 95% of the thermal conductivity of the cap tread rubber layer 1a.

  According to the pneumatic tire described above, the low thermal conductive rubber layers 21a and 21b having lower thermal conductivity than the cap tread rubber layer 1a of the tread portion 1 are provided between the main groove 7 and the belt layer 6. At the time of vulcanization, heat becomes difficult to be transmitted to portions below the low thermal conductive rubber layers 21a, 21b, and overcuring under the groove of the belt layer 6 can be prevented. As a result, the degree of vulcanization of the belt layer 6 can be made uniform regardless of the positional relationship with the main groove 7, and the adhesion between the cord of the belt layer 6 and the rubber can be improved. Therefore, the durability of the pneumatic tire can be improved.

  In the above embodiment, the low heat conductive rubber layers 21a and 21b are attached to all the main grooves 7 extending in the tire circumferential direction in the tread portion 1. However, such low heat conductive rubber layers 21a and 21b are not necessarily all. It is not necessary to attach to the main groove 7, and it may be only a part where overcuring is expected. Of course, it is possible to attach a low thermal conductive rubber layer to grooves other than the main groove extending in the tire circumferential direction.

  In a pneumatic tire in which the tire size is 11R22.5, a belt layer is embedded in the tread portion, and a groove is provided in the tread portion, the cap tread rubber of the tread portion between a part of the grooves and the belt layer A low thermal conductivity rubber layer having a thermal conductivity lower than that of the layer was provided, and a test tire in which no low thermal conductivity rubber layer was provided between the other grooves and the belt layer was molded and vulcanized. At that time, the belt layer temperature (A) and the equivalent vulcanization degree (a) below the groove not provided with the low thermal conductive rubber layer, the belt below the groove provided with the low thermal conductive rubber layer. The temperature (B) of the layer and the equivalent vulcanization degree (b), the temperature (C) of the belt layer under the shoulder block and the equivalent vulcanization degree (c) were measured. The result is shown in FIG. However, in FIG. 2, the units of temperature and equivalent vulcanization degree are omitted.

  As shown in FIG. 2, the belt layer temperature (A) increased rapidly under the groove not provided with the low thermal conductive rubber layer, and the final equivalent vulcanization degree (a) was the highest. . In addition, under the shoulder block, the belt layer temperature (C) rose slowly and the final equivalent vulcanization degree (c) was the lowest. On the other hand, the temperature (B) and the equivalent vulcanization degree (b) of the belt layer below the groove provided with the low thermal conductive rubber layer are the values below the groove where the low thermal conductive rubber layer is not provided. It was lower than the temperature (A) of the belt layer and the equivalent vulcanization degree (a). That is, the equivalent vulcanization degree of the belt layer has been optimized by adding a low thermal conductive rubber layer.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is a graph which shows the relationship (heat history) of the vulcanization time of belt layer, temperature, and an equivalent vulcanization degree.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 1a Cap tread rubber layer 1b Under tread rubber layer 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 7 Groove 9-11 Reinforcement layer 21a, 21b Low heat conductive rubber layer

Claims (5)

In a pneumatic tire in which a belt layer is embedded in the tread portion and a groove is provided in the tread portion, a low thermal conductive rubber layer having a lower thermal conductivity than the cap tread rubber layer of the tread portion is formed as the groove and the belt layer. Pneumatic tire selectively provided between the two. The pneumatic tire according to claim 1, wherein the low thermal conductive rubber layer is disposed in a portion exposed on a surface of the groove. The pneumatic tire according to claim 1, wherein the low thermal conductivity rubber layer is disposed between the cap tread rubber layer and the belt layer. 2. The pneumatic tire according to claim 1, wherein the low thermal conductive rubber layer is disposed in a portion exposed on a surface of the groove and is disposed between the cap tread rubber layer and the belt layer. The pneumatic tire according to any one of claims 1 to 4, wherein the thermal conductivity of the low thermal conductivity rubber layer is 40% to 95% of the thermal conductivity of the cap tread rubber layer.

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