JP5740932B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that obtains high steering stability while maintaining low rolling resistance performance.

  For example, the pneumatic tire described in Patent Document 1 attempts to reduce rolling resistance. In this pneumatic tire, a cap ply having a cord extending in the tire circumferential direction is disposed between the tread rubber and the belt layer. In this cap ply, a rubber composition in which 1 to 10 parts by weight of short fibers oriented in the tire circumferential direction is blended with 100 parts by weight of a diene rubber as a topping rubber for covering the cord. Such a pneumatic tire uses the above rubber composition for the top ply rubber of the cap ply, so that the restraining force in the tire width direction is not changed, so that the ride comfort is not sacrificed and the restraint in the tire circumferential direction is restricted. I am trying to increase the force and reduce rolling resistance.

  Further, for example, the pneumatic tire described in Patent Document 2 is intended to ensure or improve steering stability. In this pneumatic tire, the belt layer is covered with a topping rubber made of short fiber-containing rubber in which short fibers are contained in a rubber base material on both sides of a cord array in which metal monofilament cords are aligned. Such pneumatic tires are intended to increase the rigidity of the inner surface of the belt without increasing the number of cords to be driven, and achieve weight reduction while ensuring or improving steering stability.

JP 2006-76407 A JP 2002-120513 A

  In recent years, there has been a demand for pneumatic tires having low rolling resistance performance and low fuel consumption and high steering stability.

  The present invention has been made in view of the above, and an object thereof is to provide a pneumatic tire capable of obtaining high steering stability while maintaining low rolling resistance performance.

  In order to solve the above-described problems and achieve the object, the pneumatic tire of the present invention has a cord disposed at a predetermined angle with respect to the tire circumferential direction on the outer side in the tire radial direction of the carcass layer of the tread portion. In a pneumatic tire in which a belt layer having at least a pair of cross belts and a reinforcing belt having a cord having a larger angle with respect to a tire circumferential direction than a cord of the cross belt on the inner side in the tire radial direction of the cross belt, 100 parts by weight of vulcanizable rubber made of natural rubber, or a combination of at least two of natural rubber, synthetic polyisoprene rubber, synthetic polybutadiene and styrene-butadiene rubber, on the coat rubber covering the cord in at least one of the belt layers On the other hand, a master bag made of para-aramid fiber and stearic acid The is characterized by using the rubber composition having less than 0.2 part by weight to 3.0 parts by weight.

  According to this pneumatic tire, by using the rubber composition as a coat rubber for covering a cord in at least one of the belt layers, heat generation in the tread portion can be suppressed and low rolling resistance performance can be maintained. And the elastic modulus of a tread part can be improved and steering stability can be improved.

  The pneumatic tire of the present invention is characterized in that the rubber composition is used as a coat rubber for covering a cord in the reinforcing belt.

  According to this pneumatic tire, the cord of the reinforcing belt has a larger angle with respect to the tire circumferential direction than the cross belt, and approximates the angle of the cord of the carcass layer. That is, the reinforcing belt in the belt layer assists the movement of the carcass layer and contributes to the improvement of steering stability. As a result, by using the rubber composition for the coated rubber covering the cord in the reinforcing belt, the effect of improving the steering stability while maintaining the low rolling resistance performance can be remarkably obtained.

  In the pneumatic tire of the present invention, the coated rubber has a loss tangent tan δ measured at 60 [° C.] of 0.14 or less and an elastic modulus E1 measured at 60 [° C.] of 9.0 [MPa]. It is the above.

  By setting the loss tangent tan δ to 0.14 or less, it becomes possible to further maintain low heat generation, and by setting the elastic modulus E1 to 9.0 [MPa] or more, the steering stability can be further improved. It becomes possible. That is, according to this pneumatic tire, the effect of improving the steering stability while maintaining the low rolling resistance performance can be remarkably obtained.

  The pneumatic tire of the present invention is characterized in that the rubber composition is used as a coat rubber for covering a cord in the cross belt.

  According to this pneumatic tire, the cross belt suppresses the diameter growth of the pneumatic tire. That is, the cross belt reduces distortion in the tire radial direction of the pneumatic tire and contributes to improvement of durability. As a result, durability can be further improved by using the rubber composition for the coated rubber covering the cords in the cross belt. In addition, since the rubber composition has low heat generation, thermal deterioration can be suppressed, and low rolling resistance can be achieved by suppressing shear strain between the belt layers.

  The pneumatic tire according to the present invention can obtain high steering stability while maintaining low rolling resistance performance.

FIG. 1 is a partially cut meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a partially cut meridian cross-sectional view of a pneumatic tire according to the present embodiment. In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side. Means the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction means the side toward the tire equator plane C (tire equator line) in the tire width direction, and the outer side in the tire width direction means the tire width direction. Is the side away from the tire equatorial plane C. The tire equator plane C is a plane that is orthogonal to the rotation axis and passes through the center of the tire width of the pneumatic tire 1. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane C in the tire width direction. The tire equator line is a line on the tire equator plane C and along the circumferential direction of the pneumatic tire 1. In the present embodiment, the same sign “C” as that of the tire equator plane is attached to the tire equator line. In addition, since the pneumatic tire 1 described below is configured to be substantially symmetric with respect to the tire equatorial plane C, the pneumatic tire 1 is cut on a plane passing through the rotation axis of the pneumatic tire 1. In the meridional sectional view (FIG. 1), only one side of the tire equatorial plane C (right side in FIG. 1) is shown and only one side is described, and the other side (left side in FIG. 1) is described. Omitted.

  The pneumatic tire 1 of the present embodiment has a tread portion 2 as shown in FIG. The tread portion 2 is made of a rubber material (tread rubber), is exposed at the outermost side in the tire radial direction of the pneumatic tire 1, and the surface thereof is the contour of the pneumatic tire 1. The surface of the tread portion 2 is formed as a tread surface 21 that is a contact surface that comes into contact with the road surface when a vehicle (not shown) on which the pneumatic tire 1 is mounted travels.

  The tread surface 21 is provided with a plurality of circumferential main grooves 22 extending along the tire circumferential direction. The tread surface 21 extends along the tire circumferential direction by a plurality of circumferential main grooves 22, and a plurality of rib-like land portions 23 parallel to the tire equator line C are formed. Although not clearly shown in the drawing, the tread surface 21 may be provided with lug grooves that intersect the tire circumferential direction for each land portion 23. Further, although not shown in the figure, the tread surface 21 may be provided with sipes for each land portion 23.

  Further, the pneumatic tire 1 according to the present embodiment includes a carcass layer 6 and a belt layer 7 as shown in FIG.

  The carcass layer 6 is configured such that each tire width direction end portion is folded back from the tire width direction inner side to the tire width direction outer side by a pair of bead cores (not shown), and is wound around in a toroidal shape in the tire circumferential direction. It constitutes. The carcass layer 6 is composed of at least one layer, and a carcass cord (not shown) arranged in parallel in the tire circumferential direction along the tire meridian direction at an angle of 90 degrees (± 5 degrees) with respect to the tire circumferential direction. ) Is coated with a coat rubber. The carcass cord is made of steel or organic fiber (polyester, rayon, nylon, etc.).

  The belt layer 7 has a multilayer structure in which a plurality of belts are laminated, and is disposed inside the tread portion 2 on the outer side in the tire radial direction, which is the outer periphery of the carcass layer 6, and covers the carcass layer 6 in the tire circumferential direction. The belt layer 7 of the present embodiment is formed by laminating at least three belts 71, 72, 73 from the inner side in the tire radial direction to the outer side in the tire radial direction. In the belt layer 7, the belt 71 disposed on the innermost side in the tire radial direction is a reinforcing belt, and a plurality of cords (parallel to each other at a predetermined angle (for example, 40 degrees to 70 degrees) with respect to the tire circumferential direction) (Not shown) is coated with a coat rubber. The belts 72 and 73 disposed on the outer side in the tire radial direction of the belt 71 are a pair of cross belts, and a plurality of cords arranged in parallel at a predetermined angle (for example, 15 degrees to 30 degrees) with respect to the tire circumferential direction. (Not shown) is coated with a coat rubber. The belts 72 and 73 are provided so that the cords are inclined and crossed in opposite directions. The cords of the belts 71, 72, 73 are made of steel or organic fibers (polyester, rayon, nylon, etc.).

  That is, the belt layer 7 includes a pair of cross belts 72 and 73 having cords arranged at a predetermined angle with respect to the tire circumferential direction, and the cross belts 72 and 73 on the inner side in the tire radial direction of the cross belts 72 and 73. And at least a reinforcing belt 71 having a cord whose angle with respect to the tire circumferential direction is larger than that of the cord.

  In the pneumatic tire 1 having such a configuration, at least two of natural rubber, natural rubber, synthetic polyisoprene rubber, synthetic polybutadiene, and styrene-butadiene rubber are coated rubber that covers the cord in at least one layer of the belt layer 7. A rubber composition having a masterbatch composed of para-aramid fibers and stearic acid of 0.2 parts by weight or more and less than 3.0 parts by weight with respect to 100 parts by weight of a vulcanizable rubber made of a combination is used.

  A rubber composition having a masterbatch made of para-aramid fiber and stearic acid in an amount of 0.2 parts by weight or more and less than 3.0 parts by weight with respect to 100 parts by weight of the vulcanizable rubber is used as a coating rubber for the belt layer 7 The inventors have found that the elastic modulus can be improved while maintaining low exothermicity as compared with conventional rubber compositions.

  That is, according to the pneumatic tire 1 of the present embodiment, the rubber composition is used for the coat rubber that covers the cord in at least one layer of the belt layer 7, thereby suppressing heat generation in the tread portion 2 and reducing the heat generation. It becomes possible to maintain the rolling resistance performance, and it is possible to improve the handling stability by improving the elastic modulus of the tread portion 2.

  In the pneumatic tire 1 of the present embodiment, the rubber composition is used for the coat rubber that covers the cord in the reinforcing belt 71.

  The angle of the cord of the reinforcing belt 71 with respect to the tire circumferential direction is larger than that of the intersecting belts 72 and 73 and approximates the angle of the cord of the carcass layer 6. That is, the reinforcing belt 71 in the belt layer 7 assists the movement of the carcass layer 6 and contributes to the improvement of steering stability. As a result, by using the rubber composition for the coated rubber covering the cord in the reinforcing belt 71, it is possible to obtain a remarkable effect of improving the steering stability while maintaining the low rolling resistance performance.

  Further, in the pneumatic tire 1 of the present embodiment, the coated rubber of the belt layer 7 has a loss tangent tan δ measured at 60 [° C.] of 0.14 or less and an elastic modulus E1 measured at 60 [° C.]. It is preferable that it is 9.0 [MPa] or more.

  By setting the loss tangent tan δ to 0.14 or less, it becomes possible to further maintain low heat generation, and by setting the elastic modulus E1 to 9.0 [MPa] or more, the steering stability can be further improved. It becomes possible. That is, according to the pneumatic tire 1, it is possible to obtain a remarkable effect of improving the steering stability while maintaining the low rolling resistance performance. In addition, as for the coating rubber | gum of the belt layer 7, it is more preferable that the loss tangent tan-delta measured at 60 [degreeC] is 0.05-0.14. If the loss tangent tan δ is 0.05 or more, low exothermicity can be maintained without impairing the elongation of the coated rubber, and both durability and low exothermicity can be achieved.

  In the pneumatic tire 1 of the present embodiment, the rubber composition is used for the coat rubber that covers the cords in the cross belts 72 and 73.

  The cross belts 72 and 73 suppress the diameter growth of the pneumatic tire 1. That is, the cross belts 72 and 73 reduce distortion in the tire radial direction of the pneumatic tire 1 and contribute to improvement of durability. As a result, the durability can be further improved by using the rubber composition for the coat rubber covering the cords of the cross belts 72 and 73. Moreover, since the rubber composition has low heat generation, it is possible to suppress thermal degradation, and it is possible to reduce rolling resistance by suppressing shear strain between the belt layers 7. .

  In the present embodiment, performance tests relating to steering stability performance, low rolling resistance performance, and belt-to-belt separation resistance performance were performed on a plurality of types of pneumatic tires having different conditions (see FIG. 2). In this example, the loss tangent tan δ and the storage elastic modulus E1 are obtained by molding a rubber composition into a sheet and producing a vulcanized rubber sheet having a thickness of 2 [mm] under a vulcanization condition of 160 [° C.] for 20 minutes. The produced vulcanized rubber sheet was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, measuring temperature 60 [° C.], frequency 20 [Hz], initial strain (elongation) 10 [%], amplitude ± 2 [ %].

  In this performance test, a heavy-duty pneumatic tire having a tire size of 275 / 80R22.5 was assembled to a regular rim and filled with a regular internal pressure as a test tire. The regular rim here refers to “standard rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO.

  The evaluation method is a steering stability performance test. The test tire is mounted on a heavy load test vehicle having a total vehicle weight of 25 [t] (6 × 2), and steering is performed on a dry road during lane change and cornering. The sensory evaluation by a test driver was performed on the stability and stability during straight running. Based on this sensory evaluation, index evaluation is performed with the conventional example as a reference (100). This evaluation shows that the larger the index, the better the steering stability.

  The performance test of the low rolling resistance performance was performed at a speed of 80 [km / h] on the above-mentioned test tire to which a load (30.89 [kN]) was applied, using a drum type rolling resistance tester having a drum diameter of 1707 [mm]. The rolling resistance is measured. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation shows that rolling resistance decreases as the index increases.

  In the performance test of the belt-to-belt separation resistance, the tire is destroyed by increasing the load by 10 [%] of the normal load from the normal load every step (every 24 hours) at a traveling speed of 45 km / h. Measured at mileage up to. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation shows that the larger the index, the longer the travel distance and the better the belt-to-belt separation resistance. The normal load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

  The pneumatic tires of the conventional example, Examples 1 to 3 and the comparative example are rubber compositions that form the coat rubber of the belt layer. The vulcanizable rubber is natural rubber (made in Thailand: STR20), zinc oxide (positive Made by the same chemical industry: Zinc oxide 3 types), anti-aging agent (made by FLEXSYS: SANTOFLEX 6PPD), sulfur (made by Akzo Nobel: made by Christex HS OT 20), cobalt salt (Dainippon Ink Chemical Co., Ltd.) Product: COBALT NAPHYHENATE (10% cobalt naphthenate)), vulcanization accelerator (manufactured by Ouchi Shinsei Chemical Co., Ltd .: Noxeller DZ), carbon black (manufactured by Showa Cabot Co., Ltd .: N326) are blended as shown in FIG. ing.

  The pneumatic tires of Examples 1 to 3 and the comparative example use a masterbatch made of para-aramid fiber and stearic acid (manufactured by Teijin Limited: Sulfuron (registered trademark) 3001). In the conventional pneumatic tire, the master batch is not used.

  Moreover, the pneumatic tires of Examples 1 to 3 have a master batch in a range of 0.2 parts by weight or more and less than 3.0 parts by weight with respect to 100 parts by weight of the vulcanizable rubber. On the other hand, the pneumatic tire of the comparative example has 5 parts by weight of the master batch with respect to 100 parts by weight of the vulcanizable rubber.

  As shown in the test results of FIG. 2, it can be seen that the pneumatic tires of Examples 1 to 3 have improved handling stability resistance and low rolling resistance performance. Moreover, it turns out that the pneumatic tire of Example 1 and Example 3 is further improving the belt interlayer separation performance.

  As described above, the pneumatic tire according to the present invention is suitable for obtaining high steering stability while maintaining low rolling resistance performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 21 Tread surface 22 Circumferential main groove 23 Land part 6 Carcass layer 7 Belt layer 71 Reinforcement belt 72,73 Cross belt C Tire equatorial plane (tire equatorial line)

Claims (4)

A pair of cross belts having cords arranged at a predetermined angle with respect to the tire circumferential direction on the outer side in the tire radial direction of the carcass layer of the tread portion, and the cords of the cross belts on the inner side in the tire radial direction of the cross belts In a pneumatic tire in which a belt layer having at least a reinforcing belt having a cord having a large angle with respect to the tire circumferential direction is disposed,
The coated rubber covering the cord in at least one of the belt layers can be vulcanized by at least two selected from the group consisting of natural rubber, synthetic polyisoprene rubber, synthetic polybutadiene and styrene-butadiene rubber, or natural rubber. A pneumatic tire characterized by using a rubber composition having a master batch composed of para-aramid fiber and stearic acid in an amount of 0.2 to 3.0 parts by weight with respect to 100 parts by weight of rubber.   The pneumatic tire according to claim 1, wherein the rubber composition is used as a coated rubber that covers a cord in the reinforcing belt.   The coated rubber has a loss tangent tan δ measured at 60 [° C] of 0.14 or less and an elastic modulus E1 measured at 60 [° C] of 9.0 [MPa] or more. The pneumatic tire according to 1 or 2.   The pneumatic tire according to any one of claims 1 to 3, wherein the rubber composition is used for a coat rubber that covers a cord in the cross belt.

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