JP2009149176A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire enhanced in operation stability without totally causing the deterioration of riding comfortability and an increase of noise by suppressing an increase of rigidity in a tire vertical direction as much as possible although rigidity in a tire circumferential direction is increased. <P>SOLUTION: The pneumatic tire has a bead buried with a pair of bead cores; a side wall continued to an outer side in a radial direction of the bead; and a tread laid between the side walls, and has a bead reinforcement insert layer extending from the neighborhood of the bead core of the bead to the side wall. The bead reinforcement insert layer is formed by arranging a plurality of steel single wires in parallel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and particularly intends to improve steering stability without causing a decrease in ride comfort and an increase in noise.

  Conventionally, various means have been taken to improve the steering stability of a tire, and among them, increasing the rigidity in the circumferential direction of the tire is known as an effective means.

As such means, Patent Document 1 discloses a technique in which “a bead reinforcing layer in which a cord extends in a direction substantially perpendicular to the carcass cord in a region extending from the bead portion to the side center portion” (Claim 1). Has been proposed.
JP 2004-58807 A

Patent Document 2 discloses, in a region extending from the bead portion to the sidewall portion, “a cloth-like body in which a cord made of steel and a cord made of organic fiber are mixed and arranged in parallel” (Claim 1), A technique of arranging as a bead portion reinforcing layer has been proposed.
JP 02-225112 A

  The techniques of Patent Document 1 and Patent Document 2 described above are intended to increase rigidity in the tire circumferential direction and improve steering stability by disposing a bead portion reinforcing layer as described above.

  However, in the conventional pneumatic tire in which the bead portion reinforcing layer is arranged, the rigidity in the tire longitudinal direction increases with the improvement in the rigidity in the tire circumferential direction, so that the riding comfort is reduced and the tire noise is increased. There was a problem.

  The present invention advantageously solves the above problem and increases the rigidity in the tire circumferential direction, but suppresses the increase in the rigidity in the tire vertical direction as much as possible, thereby reducing almost no decrease in ride comfort and noise. An object of the present invention is to provide a pneumatic tire with improved handling stability without incurring.

  Now, as a result of intensive studies to achieve the above object, the inventor has conventionally used a twisted cord as a constituent member of the bead portion reinforcing layer, which causes a decrease in ride comfort and an increase in noise. I found out that it was the cause. That is, in Patent Document 1, a steel cord obtained by twisting a plurality of steel single wires is used as a constituent member of a bead reinforcement layer. In Patent Document 2, a plurality of steel wires are used as a constituent member of a bead portion reinforcing layer. An organic fiber cord formed by bundling a number of steel cords and filaments twisted together is used. However, it has been found that when the rigidity in the tire circumferential direction is increased by using the above-described twisted cord as a constituent member of the bead portion reinforcing layer, the rigidity in the tire longitudinal direction is inevitably increased.

Therefore, in order to solve this problem, further investigations were made, and as a constituent member of the bead portion reinforcing layer, a steel single wire was used instead of a twisted cord, that is, the steel single wire was used as a constituent member in parallel in the reinforcing layer. The knowledge that the above problem can be advantageously solved by arranging them has been obtained.
The present invention is based on the above findings.

That is, the gist of the present invention is as follows.
(1) It has a bead part which embeds a pair of bead cores, a side wall part which continues to the diameter direction outside of the bead part, and a tread part which straddles between the side wall parts, from the bead core neighborhood of the bead part A pneumatic tire comprising a bead portion reinforcing insert layer extending to a sidewall portion, wherein the bead portion reinforcing insert layer is formed by arranging a plurality of single steel wires in parallel.

(2) When the intersection of the circumference around the tire rotation axis and the steel single wire is assumed, the angle between the tangent of the circumference and the steel single wire at this intersection is 30 to 70 °, The pneumatic tire according to (1) above.

(3) The pneumatic as described in (1) or (2) above, wherein the bead portion reinforcing insert layer is disposed at a height of 20 to 60% of the cross-sectional height of the tire from the vicinity of the bead core. tire.

(4) The pneumatic tire according to any one of (1) to (3), wherein the bead portion reinforcing insert layer is a multistage arrangement of layers in which a plurality of steel single wires are arranged in parallel.

  According to the present invention, the bead portion reinforcing insert layer has a structure in which steel single wires are arranged in parallel, thereby increasing the rigidity in the tire circumferential direction without increasing the rigidity in the tire vertical direction. As a result, the steering stability can be improved with almost no decrease in ride comfort and an increase in noise.

Hereinafter, the pneumatic tire of the present invention will be specifically described with reference to the drawings.
FIG. 1 shows a cross section of the tire in the width direction. Since the pneumatic tire according to the present invention has a symmetrical structure with the equator plane O in between, only one side centered on the equator plane O is shown in FIG. In FIG. 1, reference numeral 1 is a bead core, 2 is a carcass extending in a toroidal shape between the bead cores 1, 2a indicates a main body of the carcass, and 2b indicates a folded portion of the carcass. 3 is a belt disposed outside the carcass 2 in the tire radial direction, 4 is a bead portion in which the bead core 1 is embedded, 5 is a side wall portion continuous to the outside in the radial direction of the bead portion 4, and 6 is straddled between the side wall portions 5. The tread part.
And 7 is a bead part reinforcement insert layer arrange | positioned in the area | region ranging from the bead core 1 vicinity of the bead part 4 to the sidewall part 5, and 8 is the steel single wire as the component. Reference numeral 9 denotes a pneumatic tire, 10 denotes an applicable rim, and 10a denotes a rim flange.

  As shown in the figure, the present invention has the greatest feature in that a plurality of steel single wires 8 are arranged in parallel as constituent members of the bead portion reinforcing insert layer 7.

  Thus, the in-plane shear rigidity of the bead portion reinforcing insert layer 7 can be improved by arranging a plurality of single steel wires in parallel as the bead portion reinforcing insert layer 7. On the other hand, an increase in out-of-plane bending rigidity can be suppressed.

  Here, the in-plane shear rigidity and the out-of-plane bending rigidity acting on the bead portion reinforcing insert layer 7 will be described with reference to FIGS. In addition, the bead part reinforcement insert layer 7 shown to the figure is the figure which showed the surface seen from the tire width direction toward the tire radial direction outer side.

  Here, the in-plane shear rigidity is a force that resists deformation that occurs in the width direction (circumferential direction of the tire) of the bead portion reinforcing insert layer 7 as indicated by the arrow in FIG. The out-of-plane bending rigidity means a force that resists deformation that occurs in a direction (longitudinal direction of the tire) perpendicular to the width direction of the bead portion reinforcing insert layer 7 as indicated by an arrow in FIG. To do.

  In the present invention, for example, as shown in FIG. 3A, a plurality of single steel wires 8 (two bundles of six in the illustrated example) are arranged in parallel to form a bead portion reinforcing insert layer 7. On the other hand, conventionally, as shown in FIGS. 3B and 3C, a so-called twisted cord 11 (in the illustrated example, five twists and three twists) is used as a constituent member of the bead portion reinforcing insert layer 7. The bead portion reinforcing insert layer 7 was used.

  However, as shown in FIGS. 3B and 3C, the bead portion reinforcing insert layer 7 using a twisted cord is obtained by twisting a single steel wire, although the in-plane shear rigidity shown in FIG. 2A is improved. Since the twisted cords having a large diameter and increased rigidity are used, the out-of-plane bending rigidity shown in FIG.

  In this regard, as shown in FIG. 3A, in the case where a plurality of steel single wires 8 are arranged in parallel according to the present invention, the six wires are integrated and have substantially the same in-plane shear rigidity as that of the stranded cord. On the other hand, since it is used as a single steel wire (thin wire) without being twisted, an increase in out-of-plane bending rigidity can be effectively suppressed as compared with a twisted cord.

  Here, as shown in FIG. 3 (a), the bead portion reinforcing insert layer shows an example in which two bundles are arranged in parallel with six steel single wires as one bundle. If the advantageous effect is obtained, the number of bundles and the arrangement of the bundles can be adjusted. Further, a plurality of single steel wires can be separated from each other, and the cords can be arranged in parallel with a uniform code interval.

  Furthermore, in order to obtain the desired rigidity in the tire circumferential direction, the number of single steel wires arranged in the bead portion reinforcing insert layer is about 22 to 36 per unit width (cm) of the bead portion reinforcing insert layer. It is preferable.

  That is, if it is less than 22, the in-plane shear stiffness may be lower than that of a twisted cord, for example, 3 strands. On the other hand, if it exceeds 36, the out-of-plane bending rigidity is improved, so that the ride comfort is reduced. Suppressive effect is small.

  Next, as shown in FIG. 4, when an intersection point P of the circumference C around the tire rotation axis and the steel single wire 8 is assumed, the tangent line L of the circumference C at the intersection P and the steel single wire 8 is sandwiched. The angle α is preferably 30 to 70 °.

  That is, if the included angle α is less than 30 °, it is difficult to expand the tire in the lateral direction at the time of manufacturing the tire, and it may be difficult to maintain the shape. On the other hand, if the included angle α exceeds 70 °, In addition, the in-plane shear rigidity is less likely to be exhibited, and the improvement in rigidity in the tire circumferential direction may be reduced.

  Moreover, it is preferable to arrange | position the bead part reinforcement insert layer 7 from the bead core 1 vicinity to the height of 20 to 60% of the cross-sectional height H of a tire. Here, the cross-sectional height H is a cross-sectional height defined in JATMA YEAR BOOK and means 1/2 of the difference between the outer diameter of the tire and the rim diameter.

  That is, when the height is less than 20% of the cross-sectional height H, there is a possibility that sufficient rigidity cannot be improved by adding the bead portion reinforcing insert layer, while the height is 60% of the cross-sectional height H. Exceeding the value tends to concentrate strain between the radially outer end portion of the bead portion reinforcing insert layer and the tire shoulder portion, which may cause failure in the portion.

  The vicinity of the bead core 1 means a region from the edge of the bead core 1 to the vicinity of the rim flange.

  Furthermore, although the example which made the bead part reinforcement insert layer 7 1 step was shown in the pneumatic tire shown in FIG. 1, not only this but a thing which consists of multiple steps may be sufficient. By making the bead portion reinforcing insert layer 7 into a plurality of steps, or by attaching a cross so that the steel single wires 8 intersect each other, the circumferential rigidity in both directions during tire rotation is greatly improved. There are advantages.

  By disposing the bead portion reinforcing insert layer having the above-described configuration in the pneumatic tire, the rigidity in the tire circumferential direction is improved and the increase in the rigidity in the tire vertical direction is suppressed. Improved steering stability is achieved without incurring an increase in noise.

  Here, although the example which has arrange | positioned the bead part reinforcement insert layer 7 in the tire width direction inner side of the carcass folding | turning part 2b was shown in FIG. 1, if the advantageous effect of this invention is acquired, it will be limited to this arrangement | positioning is not.

  A tire having a basic structure as shown in FIG. 1 was used, and a pneumatic tire (size 225 / 45R18) was prototyped under various specifications shown in Table 1. In addition, what was shown to Fig.3 (a), (b) and (c) was used for the bead part reinforcement insert layer. In order to evaluate the longitudinal stiffness, lateral stiffness and circumferential stiffness of the tire thus obtained, the tire longitudinal spring, lateral spring and circumferential spring were investigated. In addition, the obtained tire was incorporated into an applicable rim and mounted on a test vehicle, and the steering stability, ride comfort and noise were investigated. These results are shown in Table 1.

  For the longitudinal spring of the tire, the axial force and the amount of deflection were measured when the tire was incorporated into an applied rim, an internal pressure of 220 kPa was applied, and a load was applied to the tire and pressed against a flat plate. The lateral spring and the circumferential spring were investigated by measuring and calculating the displacement amount and the axial force when the displacement was applied in the tire width direction and the circumferential direction with a load of 3,92 kN. The survey results were indexed with the result of Comparative Example 1 as 100. Here, it shows that each rigidity is improving, so that an index value is large.

  In addition, the steering stability and ride comfort were evaluated by a test driver on a prescribed test course with a test vehicle equipped with tires with an internal pressure of 230 kPa front tire and 220 kPa rear tire. The evaluation is A, B, and C in the order of goodness.

  The noise was investigated by making a comprehensive judgment using the feeling obtained by the test driver and the results obtained from the instrument data in the same manner as described above.

  In the evaluation of steering stability, ride comfort and noise shown in Table 1, A has a sense of achievement of the target level, B is partially unachieved at the target level, and C is largely unachieved at the target level It shows that. The target level of the present invention is all A.

  From Table 1, although the comparative example 1 is excellent in riding comfort and noise, since the bead portion reinforcing insert layer is not used, the steering stability is poor due to the low circumferential spring. Moreover, since the conventional examples 1 and 2 use the twisted cord as the constituent member of the bead portion reinforcing insert layer, the circumferential direction spring is increased and the steering stability is excellent. Further, since the lateral springs also increase, the ride comfort is lowered and the noise is greatly increased.

  On the other hand, since all of the invention examples can suppress the increase of the vertical spring and the horizontal spring as much as possible, and the circumferential spring can be increased, almost without causing a decrease in riding comfort and an increase in noise. Improve handling stability.

It is a figure which shows the cross section of the width direction of the pneumatic tire according to this invention. It is a figure explaining in-plane shear rigidity (a) and out-of-plane bending rigidity (b). It is a figure which shows the cross section of the width direction of the bead part reinforcement insert layer according to the prior art and this invention. It is a figure which shows the included angle (alpha) of a steel single wire and a tangent.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 2a Carcass main-body part 2b Carcass folding | turning part 3 Belt 4 Bead part 5 Side wall part 6 Tread part 7 Bead part reinforcement insert layer 8 Steel single wire 9 Pneumatic tire 10 Applicable rim 10a Rim flange 11 Steel cord

Claims (4)

  A bead portion having a pair of bead cores embedded therein, a sidewall portion continuous to the outside in the radial direction of the bead portion, and a tread portion straddling the sidewall portion, the sidewall portion from the vicinity of the bead core of the bead portion A pneumatic tire provided with a bead portion reinforcing insert layer extending in a row, wherein the bead portion reinforcing insert layer is formed by arranging a plurality of single steel wires in parallel.   When an intersection of a circumference around the tire rotation axis and the steel single wire is assumed, an angle between the tangent of the circumference and the steel single wire at the intersection is 30 to 70 °. The pneumatic tire according to 1.   The pneumatic tire according to claim 1, wherein the bead portion reinforcing insert layer is disposed at a height of 20 to 60% of a cross-sectional height of the tire from the vicinity of the bead core.   The pneumatic tire according to any one of claims 1 to 3, wherein the bead portion reinforcing insert layer is a multistage arrangement of layers in which a plurality of single steel wires are arranged in parallel.

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