JP2008307963A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of attaining enhancement of steering stability without reducing ride comfort even when a reinforcement layer is provided on an outer side in a tire width direction of a bead filler. <P>SOLUTION: The steering stability can be enhanced by the reinforcement layer 16 provided on an outer side in the tire width direction of the bead filler 13b, and a reinforcement cord 16a of the reinforcement layer 16 is formed such that rigidity of the outer side in a tire radial direction is reduced than an inner side in a tire radial direction. Therefore, bending rigidity of the side part with large deflection is not increased by rigidity of the reinforcement layer 16 and enhancement of the operation stability can be attained without reducing riding comfort. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire used in, for example, passenger cars, trucks, buses and the like.

Conventionally, as a pneumatic tire of this type, one in which a reinforcing layer is provided on the outer side in the tire width direction of a bead filler is known in order to improve handling stability (see, for example, Patent Document 1). This reinforcing layer is formed by arranging a plurality of reinforcing cords extending obliquely in the tire radial direction in the tire circumferential direction, and increases the rigidity of the side portion.
JP 2003-182320 A

  However, in the conventional pneumatic tire, the steering stability is improved by providing the reinforcing layer, but the rigidity of the portion having a large deflection in the side portion is increased by the reinforcing layer, so that there is a problem that the riding comfort is lowered. It was.

  The present invention has been made in view of the above problems, and the object of the present invention is to improve steering stability without reducing ride comfort even when a reinforcing layer is provided on the outer side of the bead filler in the tire width direction. It is to provide a pneumatic tire that can be achieved.

  In order to achieve the above object, the present invention is configured such that both ends of the carcass member in the tire width direction are folded outward in the tire width direction so as to wind up around the bead portion, and the bead filler is inclined in the tire radial direction on the outer side in the tire width direction. In a pneumatic tire provided with a reinforcing layer in which a plurality of extending reinforcing cords are arranged in the tire circumferential direction, the reinforcing cords are formed such that the outer side in the tire radial direction is lower in rigidity than the inner side in the tire radial direction.

  Thereby, while the steering stability is improved by the reinforcing layer provided on the outer side in the tire width direction of the bead filler, since the outer side in the tire radial direction of the reinforcing cord of the reinforcing layer is lower in rigidity than the inner side in the tire radial direction, The bending rigidity of the side part with large deflection is not increased by the rigidity of the reinforcing layer.

  According to the present invention, since the bending rigidity of the side part with large deflection is not increased by the rigidity of the reinforcing layer, even when the reinforcing layer is provided on the outer side in the tire width direction of the bead filler, the maneuverability is not reduced. Stability can be improved.

  1 to 6 show an embodiment of the present invention. FIG. 1 is a partial front sectional view of a pneumatic tire, FIG. 2 is a front sectional view of an essential part thereof, FIG. 3 is a side view of a reinforcing layer, and FIG. Is a radial sectional view of the reinforcing cord, FIG. 5 is a side view of the wire, and FIG. 6 is a diagram showing the test results.

  The pneumatic tire shown in the figure includes a tread portion 1 formed on the tire outer peripheral surface side, sidewall portions 2 formed on both sides in the tire width direction, and beads formed on the tire radial direction inner side of the sidewall portions 2. And a shoulder portion 4 formed between the tread portion 1 and the sidewall portion 2.

  That is, in this pneumatic tire, a sheet-like inner liner 10, a plurality of carcass members 11, and a plurality of belts 12 are formed into a cylindrical shape on a forming drum, and then the carcass member 11 is a pair of left and right bead members. The carcass member 11 is formed in a toroidal shape so as to straddle between the two, and both ends in the tire width direction of the carcass member 11 are wound from the periphery of the bead member 13 to the outer side in the tire width direction and folded back to the side wall portion 2 side. It is formed by sticking the tread member 14 and the sidewall member 15 to each other. A reinforcement layer 16 is provided on the outer side of the bead member 13 in the tire width direction.

  The inner liner 10 is made of a sheet-like rubber having airtightness, and is disposed on the inner peripheral surface side of the carcass member 11.

  The carcass member 11 is a sheet-like member in which a plurality of carcass cords are covered with rubber, and is disposed on the outer peripheral surface side of the inner liner 10.

  Each belt 12 is formed by covering a plurality of reinforcing cords made of steel cords, high-strength fibers, and the like with sheet-like rubber, and is disposed on the carcass member 11 so as to overlap each other in the tire radial direction.

  The bead member 13 includes a bead core 13a formed by bundling wires such as metal wires, and a bead filler 13b formed of rubber having a substantially triangular cross section. The bead filler 13b is disposed on the outer peripheral side of the bead core 13a.

  The tread member 14 is made of rubber formed by extrusion molding, and is disposed on the outer peripheral surface side of the carcass member 11. A groove 14a having a predetermined pattern is formed on the outer peripheral surface of the tread member 14 during vulcanization molding.

  The sidewall member 15 is made of rubber formed by extrusion molding, and is disposed so as to cover both sides of the carcass member 11 in the tire width direction.

  The reinforcing layer 16 is formed by arranging a sheet-like member in which a plurality of reinforcing cords 16a are covered with rubber on the outer side in the tire width direction of the bead filler 13b, and each reinforcing cord 16a extends in the tire circumferential direction so as to extend obliquely in the tire radial direction. Are arranged at equal intervals. The reinforcing cord 16a has a twisted structure of four wires 16b made of a steel cord, high-strength fibers, etc., and each wire 16b is formed so that the twist pitch is gradually smaller on the outer side in the tire radial direction than on the inner side in the tire radial direction. Has been. As a result, the reinforcing cord 16a is configured so that the outer side in the tire radial direction is the inner side in the tire radial direction due to the difference in the twisting pitch of each wire 16b so that the coil spring with a narrow helical pitch has a weaker spring force than the coil spring with a wide helical pitch. The rigidity is lower than that. In this case, as shown in FIG. 5, the wire 16b is formed such that the minimum twist pitch P1 on the outer side in the tire radial direction is 30% to 80% of the maximum twist pitch P2 on the inner side in the tire radial direction. The number of the wires 16b of the reinforcing cord 16a may be 2 or more and 6 or less, and the wire 16b may have an outer diameter of 0.10 mm or more and 0.35 mm or less.

  In the above configuration, the reinforcing layer 16 is disposed outside the bead filler 13b in the tire width direction, and the folded portion of the carcass member 11 is disposed outside the reinforcing layer 16 in the tire width direction. The outer end portion in the tire radial direction of the reinforcing layer 16 is disposed on the outer side in the tire radial direction with respect to the outer end portion in the tire radial direction of the bead filler 13b, and is disposed on the inner side in the tire radial direction with respect to the folded end portion of the carcass member 11. The In this case, the height of the reinforcing layer 16 is S, the height of the bead filler 13b is F, and the height of the folded end of the carcass member 11 is from the outer end in the tire radial direction of the bead core 13a toward the outer side in the tire radial direction. When T, the reinforcing layer 16 is formed so as to satisfy (F + 3 mm) ≦ S ≦ (T-11 mm). When the tire cross-section height is H, the reinforcing layer 16 is formed so as to satisfy 0.25 ≦ (S / H) ≦ 0.55. The tire cross-sectional height H is a tire cross-sectional height in a state where the tire 10 is filled with a normal internal pressure defined by JATMA and a normal load is applied.

  Here, when Examples 1 and 2 of the present invention and Comparative Examples 1 and 2 were tested for steering stability and riding comfort, the results shown in FIG. 6 were obtained. In Comparative Example 1, the wire twist pitch of the reinforcing cord was the same between the inner side and the outer side in the tire radial direction, and in Comparative Example 2, the wire twist pitch was larger on the outer side than the inner side in the tire radial direction. In each of Examples 1 and 2, the wire twist pitch is smaller on the outer side than on the inner side in the tire radial direction, and Example 2 has a twist pitch ratio (twist pitch on the outer side in the tire radial direction / tire) than that in Example 1. Those having a small radial inner twist pitch × 100) were used.

  In this test, a tire having a tire size of 205 / 55R16 and an air pressure of 230 kPa was mounted on a passenger car having a displacement of 2000 cc, and the sensory evaluation of the driver during straight running and lane change was indexed. Examples 1 and 2 were evaluated. In this case, it was determined that the greater the index value, the more superior. As a result of the test, both Examples 1 and 2 were superior to Comparative Examples 1 and 2.

  Thus, according to the present embodiment, the steering stability can be improved by the reinforcing layer 16 provided on the outer side in the tire width direction of the bead filler 13b, and the reinforcing cord 16a of the reinforcing layer 16 is disposed on the outer side in the tire radial direction. Because the rigidity is lower than the inner side in the tire radial direction, the bending rigidity of the side part with large deflection is not increased by the rigidity of the reinforcing layer 16, and the driving stability is improved without deteriorating the riding comfort. Can be planned.

  Further, since the outer end portion in the tire radial direction of the reinforcing layer 16 is arranged on the outer side in the tire radial direction with respect to the outer end portion in the tire radial direction of the bead filler 13b, the reinforcing layer 16 can sufficiently ensure rigidity in the tire circumferential direction. In addition, the rigidity in the tire radial direction by the bead filler 13b can be reduced, which is effective in improving riding comfort. Further, since the outer end portion in the tire radial direction of the reinforcing layer 16 is disposed on the inner side in the tire radial direction from the folded end portion of the carcass member 11, separation by the outer end portion in the tire radial direction of the reinforcing layer 16 is prevented by the carcass member 11. It is possible to improve durability.

  In this case, the height of the reinforcing layer 16 is S, the height of the bead filler 13b is F, and the height of the folded end of the carcass member 11 is from the outer end in the tire radial direction of the bead core 13a toward the outer side in the tire radial direction. When T, the reinforcing layer 16 is formed so as to satisfy (F + 3 mm) ≦ S ≦ (T−11 mm). Therefore, the difference between the height S of the reinforcing layer 16 and the height F of the bead filler 13b becomes too small. Riding comfort is not reduced, and the difference between the height S of the reinforcing layer 16 and the height T of the folded end portion of the carcass member 11 is not too small, and the durability is not improved sufficiently. Therefore, it is extremely advantageous not only for improving the steering stability, but also for improving the riding comfort and the durability.

  Further, since the reinforcing layer 16 is formed so that 0.25 ≦ (S / H) ≦ 0.55, where the tire cross-sectional height is H, the height S of the reinforcing layer 16 with respect to the tire cross-sectional height H is The steering stability by the reinforcing layer 16 does not become insufficient due to being too small, and the height S of the reinforcing layer 16 does not become too large to reduce the riding comfort. Therefore, it is extremely advantageous in achieving both improvement in handling stability and improvement in riding comfort.

  Furthermore, since the reinforcing cord 16a of the reinforcing layer 16 is formed by a twisted structure of a plurality of wires 16b, and the twist pitch of each wire 16b is formed so that the outer side in the tire radial direction is smaller than the inner side in the tire radial direction. The reinforcement cord 16a can be formed such that the rigidity in the tire radial direction outer side is lower than the tire radial direction inner side due to the difference in the twist pitch of the wire 16b, and the reinforcement cord 16a having a rigidity difference in the longitudinal direction is easily formed. be able to.

  In this case, the reinforcing cord 16a is formed so that the minimum twist pitch P1 on the inner side in the tire radial direction of each wire 16b is not less than 30% and not more than 80% of the maximum twist pitch P2 on the outer side in the tire radial direction. The rigidity difference is not so small that the effect is not insufficient, and the rigidity difference is not so large that the rigidity in the tire circumferential direction by the reinforcing layer 16 is not lowered. Therefore, it is extremely advantageous in achieving both improvement in handling stability and improvement in riding comfort.

  Moreover, since the outer diameter of the wire 16b of the reinforcing cord 16a is formed to be 0.10 mm or more and 0.35 mm or less, the outer diameter of the wire 16b is too small, and the rigidity of the reinforcing cord 16a in the tire radial direction is insufficient. In other words, the outer diameter of the wire 16b is not too large and the difference in rigidity due to the difference in twist pitch is not reduced. Accordingly, it is possible to form the reinforcing cord 16a having the optimum rigidity difference in the longitudinal direction.

  Further, since the reinforcing cord 16a is formed so that the number of the wires 16b is 2 or more and 6 or less, the number of the wires 16b is not so small that the rigidity of the reinforcing cord 16a in the tire radial direction is not insufficient. The number of wires 16b is not too large, and the difference in rigidity due to the difference in twist pitch is not reduced. Accordingly, it is possible to form the reinforcing cord 16a having the optimum rigidity difference in the longitudinal direction.

  In the embodiment described above, the folded portion of the carcass member 11 is disposed outside the reinforcing layer 16 in the tire width direction. However, some of the carcass members among the plurality of carcass members are replaced with the tire width of the reinforcing layer 16. You may make it arrange | position inside a direction.

  Moreover, in the said embodiment, although what formed the twist pitch of each wire 16b so that a tire radial direction outer side might become smaller than a tire radial direction inner side, for example, the number of wires is a tire diameter rather than a tire radial direction inner side. Reinforcement cords having other configurations may be used such that the outer side in the direction is reduced or the outer diameter of the wire is formed so that the outer side in the tire radial direction is smaller than the inner side in the tire radial direction. .

Partial front sectional view of a pneumatic tire showing an embodiment of the present invention Front sectional view of main parts of pneumatic tire Side view of reinforcement layer Radial cross section of reinforcement cord Side view of the wire Diagram showing test results

Explanation of symbols

  13a ... Bead core, 13b ... Bead filler, 11 ... Carcass member, 16 ... Reinforcement layer, 16a ... Reinforcement cord, 16b ... Wire.

Claims (8)

A plurality of reinforcing cords extending in the tire radial direction are arranged in the tire circumferential direction on the outer side in the tire width direction of the bead filler so that both ends of the carcass member in the tire width direction wind up around the bead portion. In a pneumatic tire provided with a reinforcing layer,
The pneumatic tire is characterized in that the reinforcing cord is formed such that the outer side in the tire radial direction has lower rigidity than the inner side in the tire radial direction. The outer end portion in the tire radial direction of the reinforcing layer is disposed on the outer side in the tire radial direction with respect to the outer end portion in the tire radial direction of the bead filler, and is disposed on the inner side in the tire radial direction with respect to the folded end portion of the carcass member. The pneumatic tire according to claim 1. When the height of the reinforcing layer is S, the height of the bead filler is F, and the height of the folded end of the carcass member is T from the outer end of the bead core in the tire radial direction toward the outer side in the tire radial direction, (F + 3 mm) The pneumatic tire according to claim 2, wherein a reinforcing layer is formed so as to satisfy ≦ S ≦ (T−11 mm). When the height of the reinforcing layer is S and the tire cross-section height is H from the tire radial outer end of the bead core to the tire radial outer side, 0.25 ≦ (S / H) ≦ 0.55. The pneumatic tire according to claim 1, 2, or 3, wherein a reinforcing layer is formed on the tire. The reinforcement cord is formed by a twist structure of a plurality of wires, and the twist pitch of each wire is formed so that the outer side in the tire radial direction is smaller than the inner side in the tire radial direction. The pneumatic tire according to 3 or 4. The pneumatic cord according to claim 5, wherein the reinforcing cord is formed such that the minimum twist pitch inside the tire radial direction of each wire is 30% or more and 80% or less of the maximum twist pitch outside the tire radial direction. tire. The pneumatic tire according to claim 5 or 6, wherein a wire of the reinforcing cord is formed so that an outer diameter is 0.10 mm or more and 0.35 mm or less. The pneumatic tire according to claim 5, 6 or 7, wherein the reinforcing cord is formed so that the number of wires is 2 or more and 6 or less.

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