JP2010137650A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving durability while keeping favorable controllability, stability and ride comfort, in the pneumatic tire including carcass layers separated in a tread. <P>SOLUTION: The carcass layers 4 separated in the tread portion 1 are laid between a pair of beads 3, 3, and a belt layer 6 is disposed at an outer peripheral side of the carcass layer 4 in the tread 1. Adhesive rubber layers 7 are interposed between the belt layer 6 and each divided piece 4A of the carcass layers 4. The JIS-A hardness of the adhesive rubber layer 7 is set to be larger than the JIS-A hardness of the rubber of the carcass layer 4, and the JIS-A hardness of the adhesive rubber layer 7 is set to be smaller than the JIS-A hardness of the rubber of the belt layer 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having a carcass layer divided at a tread portion, and more particularly, a pneumatic tire capable of improving durability while maintaining good driving stability and riding comfort. Regarding tires.

  In recent years, it has been proposed to divide a carcass layer in a tread portion while embedding a belt layer in the tread portion for the purpose of eliminating manufacturing problems and improving tire performance in a pneumatic tire ( For example, see Patent Document 1). In such a pneumatic tire, even if the carcass layer is divided in the tread portion, the rigid belt layer embedded in the tread portion carries the tension, so that it is possible to exhibit a sufficient internal pressure holding capability.

However, when the carcass layer is divided in the tire width direction at the tread portion, stress concentrates on the interface between the belt layer and the carcass layer, so that failure tends to occur starting from that portion. Accordingly, in a pneumatic tire having a carcass layer having a split structure, it has been proposed that a joint ply including a reinforcing cord is interposed between the belt layer and the carcass layer so that the split pieces of the carcass layer are in close contact with each other. (For example, see Patent Document 2). However, even if a splicing ply including a reinforcing cord is inserted, stress concentrates on the interface, and it is difficult to obtain a sufficient durability improvement effect.
JP 2001-187511 A Japanese Patent Laid-Open No. 10-157408

  It is an object of the present invention to provide a pneumatic tire having a carcass layer divided at a tread portion, and capable of improving durability while maintaining good steering stability and ride comfort. It is to provide.

  In order to achieve the above object, a pneumatic tire according to the present invention has a carcass layer divided by a tread portion between a pair of bead portions and a belt layer disposed on the outer periphery side of the carcass layer in the tread portion. An adhesive rubber layer is interposed between the belt layer and each segment of the carcass layer, and the JIS-A hardness of the adhesive rubber layer is larger than the JIS-A hardness of the rubber portion of the carcass layer, Further, the JIS-A hardness of the adhesive rubber layer is smaller than the JIS-A hardness of the rubber part of the belt layer.

  Here, the JIS-A hardness in the present invention is measured according to JIS K6253 “vulcanized rubber and thermoplastic rubber—how to obtain hardness”, and is measured using a type A durometer. It means durometer hardness.

  In the present invention, in a pneumatic tire having a carcass layer divided at a tread portion, an adhesive rubber layer is interposed between the belt layer and each divided piece of the carcass layer, and the JIS-A hardness of the adhesive rubber layer Is made larger than the JIS-A hardness of the rubber part of the carcass layer and smaller than the JIS-A hardness of the rubber part of the belt layer to avoid stress concentration at the interface between the belt layer and the carcass layer, The durability of the entering tire can be improved. Further, even if an adhesive rubber layer is interposed between the belt layer and each divided piece of the carcass layer, it is possible to maintain good steering stability and riding comfort.

  In the present invention, the width W1 of the portion sandwiched between the belt layer of the adhesive rubber layer and each segment of the carcass layer is preferably in a relationship of 0.1 ≦ W1 / W0 with respect to the half width W0 of the belt layer. Further, the thickness T of the portion sandwiched between the belt layer of the adhesive rubber layer and each segment of the carcass layer is preferably 0.3 mm or more and 4.0 mm or less. Furthermore, it is preferable that the overlap width W2 between the belt layer and each segment of the carcass layer is in a relation of 0.1 ≦ W2 / W0 with respect to the half width W0 of the belt layer. Thereby, durability can be effectively improved, maintaining steering stability and riding comfort satisfactorily.

  The following asymmetric structure can be adopted in a pneumatic tire in which the mounting direction of the tire front and back is specified when the vehicle is mounted. That is, the width W1 of the portion sandwiched between the belt layer of the adhesive rubber layer and each segment of the carcass layer is made different between the vehicle inner side and the vehicle outer side, and the width W1 on the vehicle outer side is relatively increased. A structure can be adopted. In this case, the steering stability can be improved. In addition, the thickness T of the portion sandwiched between the belt layer of the adhesive rubber layer and each segment of the carcass layer is made different between the vehicle inner side and the vehicle outer side, and the value of the thickness T on the vehicle outer side is relatively small. An asymmetrical structure can be adopted. In this case, the ride comfort can be improved.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire for a passenger car according to an embodiment of the present invention, wherein 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 including a plurality of carcass cords extending in the tire radial direction and a rubber portion covering the carcass cords is mounted between the pair of bead portions 3 and 3. As the carcass cord, a steel cord can be used in addition to an organic fiber cord such as a polyester cord and a nylon cord. The carcass layer 4 is divided in the tire width direction in the tread portion 1. That is, the carcass layer 4 is composed of a pair of divided pieces 4A and 4A. The ends of the carcass layer 4 on the outer side in the tire width direction of the divided pieces 4A and 4A are folded around the bead core 5 from the tire inner side to the outer side.

  On the other hand, a plurality of belt layers 6 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 6 are composed of a plurality of belt cords inclined with respect to the tire circumferential direction and rubber portions covering the belt cords, and are arranged so that the belt cords cross each other between the layers. As the belt cord, an organic fiber cord such as an aramid cord can be used in addition to a steel cord. A belt cover layer formed by winding a reinforcing cord in the tire circumferential direction may be disposed on the outer peripheral side of the belt layer 6 as necessary.

  In the pneumatic tire, an adhesive rubber layer 7 is inserted between the belt layer 6 and each divided piece 4 </ b> A of the carcass layer 4. The adhesive rubber layer 7 is composed of a rubber composition exhibiting a JIS-A hardness that is greater than the JIS-A hardness of the rubber part of the carcass layer 4 and smaller than the JIS-A hardness of the rubber part of the belt layer 6. . The difference between the JIS-A hardness of the adhesive rubber layer 7 and the JIS-A hardness of the rubber part of the carcass layer 4 or the JIS-A hardness of the rubber part of the belt layer 6 is preferably 2 points or more. Preferably it is 4 points or more.

  Thus, in the pneumatic tire provided with the carcass layer 4 divided by the tread portion 1, the adhesive rubber layer 7 is interposed between the belt layer 6 and each divided piece 4A of the carcass layer 4, and the adhesive rubber layer. 7 is made larger than the JIS-A hardness of the rubber part of the carcass layer 4 and smaller than the JIS-A hardness of the rubber part of the belt layer 6, so that the belt layer 6 and the carcass layer 4 Stress concentration on the interface can be avoided, and the durability of the pneumatic tire can be improved. In addition, even if the adhesive rubber layer 7 is interposed between the belt layer 6 and each divided piece 4A of the carcass layer 4, it is possible to maintain good steering stability and riding comfort.

  In the pneumatic tire described above, the width W1 of the portion sandwiched between the belt layer 6 of the adhesive rubber layer 7 and each divided piece 4A of the carcass layer 4 is smaller than the half width W0 of the belt layer 6 centering on the tire equator E. It is preferable to set a relationship of 0.1 ≦ W1 / W0 (see FIGS. 2 to 4). Here, if 0.1> W1 / W0, the durability improving effect is insufficient.

  Further, the thickness T of the portion sandwiched between the belt layer 6 of the adhesive rubber layer 7 and the respective divided pieces 4A of the carcass layer 4 is preferably set to 0.3 mm or more and 4.0 mm or less. Here, if the thickness T of the adhesive rubber layer 7 is less than 0.3 mm, the effect of improving the durability is insufficient, and conversely, if it exceeds 4.0 mm, the steering stability is deteriorated.

  Further, the overlap width W2 in the tire width direction between the belt layer 6 and each segment 4A of the carcass layer 4 has a relationship of 0.1 ≦ W2 / W0 with respect to the half width W0 of the belt layer 6 centering on the tire equator E. It is good to set to. Here, if 0.1> W2 / W0, the durability improving effect is insufficient.

  When importance is attached to steering stability, the adhesive rubber layer 7 is made thin and wide as shown in FIG. In this case, the width W1 of the adhesive rubber layer 7 is set to a relationship of 0.2 ≦ W1 / W0, more preferably a relationship of 0.2 ≦ W1 / W0 ≦ 0.5, and the thickness of the adhesive rubber layer 7 is set. It is desirable to set T to 0.3 mm or more and 1.5 mm or less.

  On the other hand, when importance is attached to riding comfort, the adhesive rubber layer 7 is made thick and narrow as shown in FIG. In this case, the width W1 of the adhesive rubber layer 7 is set to a relationship of 0.1 ≦ W1 / W0, more preferably 0.5 ≦ W1 / W0 ≦ 0.7, and the thickness of the adhesive rubber layer 7 is set. It is desirable to set T to 1.5 mm or more and 4.0 mm or less.

  In addition, an asymmetric structure as shown in FIG. 4 can be employed in a pneumatic tire in which the mounting direction of the tire front and back is specified when the vehicle is mounted. In FIG. 4, IN is the inside of the vehicle when the vehicle is mounted, and OUT is the outside of the vehicle when the vehicle is mounted. As shown in FIG. 4, the width W1 of the portion sandwiched between the belt layer 6 of the adhesive rubber layer 7 and each segment 4A of the carcass layer 4 is different between the vehicle inner side and the vehicle outer side. The value of W1 is relatively large. Further, the thickness T of the portion sandwiched between the belt layer 6 of the adhesive rubber layer 7 and each segment 4A of the carcass layer 4 is different between the vehicle inner side and the vehicle outer side, and the value of the thickness T on the vehicle outer side is different. Is relatively small.

  In particular, in a vehicle in which a negative camber is set, the structure on the inner side of the pneumatic tire greatly affects the ride comfort, and the structure on the outer side of the pneumatic tire greatly affects the steering stability. On the other hand, in the asymmetric structure, the adhesive rubber layer 7 disposed on the inner side of the vehicle is made thicker and narrower to improve riding comfort, while the adhesive rubber layer 7 disposed on the outer side of the vehicle is thinned. Since the steering stability is improved by increasing the width, it is possible to achieve both the steering stability and the ride comfort at a high level.

  In the tire size 225 / 45R18, a carcass layer divided by a tread portion is mounted between a pair of bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion, and the belt layer and the carcass layer Adhesive rubber layer is interposed between each piece, JIS-A hardness of adhesive rubber layer, JIS-A hardness of rubber part of carcass layer, JIS-A hardness of rubber part of belt layer, half width W0 of belt layer Table 1 shows the ratio of the width W1 of the adhesive rubber layer to W1 (W1 / W0), the ratio of the overlap width W2 of each segment of the carcass layer to the half width W0 of the belt layer (W2 / W0), and the thickness T of the adhesive rubber layer. The pneumatic tires of Examples 1 to 3 and Comparative Examples 1 and 2 set as described above were manufactured. For comparison, the tire of Conventional Example 1 having the same configuration as described above except that the adhesive rubber layer is not provided, and the carcass layer instead of the adhesive rubber layer between the belt layer and the carcass layer divided pieces. A tire of Conventional Example 2 having the same configuration as described above was prepared except that a similar cord layer was interposed.

  These test tires were evaluated for durability, handling stability, and riding comfort by the following evaluation methods, and the results are also shown in Table 1.

durability:
Each test tire was subjected to a durability performance test in accordance with JIS D4230, and then the load was increased by 15% of the initial load every 4 hours, and the travel distance until the tire failed was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. The larger the index value, the better the durability.

Steering stability:
Each test tire was assembled on a wheel having a rim size of 18 × 7.5 J and mounted on a test vehicle. The air pressure was 230 kPa, and a sensory evaluation was performed by a driver on the test course. The evaluation results are shown as an index with Conventional Example 1 as 100. The larger the index value, the better the steering stability.

Ride comfort:
Each test tire was assembled on a wheel having a rim size of 18 × 7.5 J and mounted on a test vehicle. The air pressure was 230 kPa, and a sensory evaluation was performed by a driver on the test course. The evaluation results are shown as an index with Conventional Example 1 as 100. The larger the index value, the better the ride comfort.

  As is apparent from Table 1, the tires of Examples 1 to 3 were significantly improved in durability as compared with Conventional Examples 1 and 2, and also had good steering stability and riding comfort. On the other hand, in the tires of Comparative Examples 1 and 2, the JIS-A hardness of the adhesive rubber layer is not an intermediate value between the JIS-A hardness of the rubber part of the carcass layer and the JIS-A hardness of the rubber part of the belt layer. The durability improvement effect was not obtained.

  Next, pneumatic tires of Examples 4 to 6 in which a part of the configuration of Example 2 was changed as shown in Table 2 were manufactured. In Examples 4 to 6, the sizes of the adhesive rubber layers are variously changed.

  These test tires were evaluated for durability, handling stability, and riding comfort by the above-described evaluation methods, and the results are also shown in Table 2.

  As shown in Table 2, when the adhesive rubber layer was thin and wide (Example 4), the steering stability was relatively improved. In addition, when the adhesive rubber layer was thick and narrow (Example 5), the ride comfort was relatively improved. Further, when the adhesive rubber layer disposed inside the vehicle is thick and narrow while the adhesive rubber layer disposed outside the vehicle is thin and wide (Example 6), steering stability and riding comfort are improved. Both were getting better.

1 is a meridian cross-sectional view showing a passenger car pneumatic tire according to an embodiment of the present invention. It is a meridian cross-sectional view schematically showing an example of the skeleton structure of the pneumatic tire of the present invention. It is a meridian cross-sectional view schematically showing an example of the skeleton structure of the pneumatic tire of the present invention. It is a meridian cross-sectional view schematically showing an example of the skeleton structure of the pneumatic tire of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 4A Divided piece of carcass layer 5 Bead core 6 Belt layer 7 Adhesive rubber layer

Claims (6)

  A carcass layer divided at the tread portion is mounted between a pair of bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion, and the belt layer and each divided piece of the carcass layer An adhesive rubber layer is interposed therebetween, the JIS-A hardness of the adhesive rubber layer is larger than the JIS-A hardness of the rubber part of the carcass layer, and the JIS-A hardness of the adhesive rubber layer is A pneumatic tire characterized by being smaller than the JIS-A hardness of the rubber part.   The width W1 of the portion sandwiched between the belt layer of the adhesive rubber layer and each segment of the carcass layer has a relation of 0.1 ≦ W1 / W0 with respect to the half width W0 of the belt layer. The pneumatic tire according to claim 1.   The thickness T of a portion sandwiched between the belt layer of the adhesive rubber layer and each of the divided pieces of the carcass layer is set to 0.3 mm or greater and 4.0 mm or less. The described pneumatic tire.   4. The overlap width W <b> 2 between the belt layer and each divided piece of the carcass layer has a relationship of 0.1 ≦ W <b> 2 / W <b> 0 with respect to the half width W <b> 0 of the belt layer. Pneumatic tire described in 2.   In a pneumatic tire in which the mounting direction of the tire front and back is specified when the vehicle is mounted, the width W1 of the portion sandwiched between the belt layer of the adhesive rubber layer and the divided pieces of the carcass layer is set to the vehicle inner side and the vehicle outer side. The pneumatic tire according to any one of claims 1 to 4, characterized in that the width W1 on the outside of the vehicle is relatively increased.   In a pneumatic tire in which the mounting direction of the tire front and back is specified when the vehicle is mounted, the thickness T of the portion sandwiched between the belt layer of the adhesive rubber layer and the divided pieces of the carcass layer is set to the vehicle inner side and the vehicle outer side. The pneumatic tire according to claim 1, wherein the value of the thickness T on the outside of the vehicle is relatively small.

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