JP2010115953A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of sufficiently enhancing required high pressure durability and attaining more further reduction of weight of the tire. <P>SOLUTION: The pneumatic radial tire includes: a radial carcass 5 comprising a plurality of carcass plies formed by a rubber covering layer of a polyketone fiber cord extending to be toroidal between a pair of bead cores 4 while making an angle in a range of 70-90° relative to a tire equator E and including each of three sheets of turn-up plies 5a in which respective side part portions are rolled up at a periphery of the bead core from an inner side to an outer side in a tire width direction and one sheets of down ply 5b involving a rolled-up portion 5c of the turn-up ply 5a; and a belt arranged at an outer peripheral side of a crown area of the radial carcass 5. In this case, an insert ply 9 comprising a rubber covering layer of a polyketone fiber and extending from one tire side part to the other tire side part is arranged between the turn-up ply 5a and the down ply 5b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a radial tire for an aircraft. In particular, the present invention proposes a technique for ensuring a required pressure resistance performance while realizing weight reduction of the tire.

Since radial aircraft tires are used under high internal pressure filling, a large number of carcass plies are required to ensure pressure resistance performance with a safety factor, while aircraft tires themselves are Because it is used only during takeoff and landing, it is necessary to satisfy the mutually contradictory requirements that the aircraft manufacturer demands further weight reduction. As described, the number of carcass plies can be reduced while achieving the required high-pressure durability by using a carcass ply forming member made of polyketone fiber cord with high breaking strength and rubber coating. Therefore, the tire weight was reduced.
JP 2007-190963 A

  The present invention is a pneumatic radial tire obtained by adding further improvements to the invention described in Patent Document 1 and sufficiently ensuring the required high-pressure durability and further reducing the tire weight. Is to provide.

  The pneumatic radial tire according to the present invention includes a plurality of polyketone fiber cord rubber coating layers formed toroidally between a pair of bead cores at an angle in a range of 70 to 90 ° with respect to the tire equatorial plane. The carcass ply consists of one or more turn-up plies each of which is wound around the bead core from the inner side to the outer side in the tire width direction and one or more down plies that contain the turn-up ply's hoisted part. A radial carcass including the belt and a belt disposed on the outer peripheral side of the crown region of the radial carcass, for example, a sub belt composed of two or more belt layers in which cords cross each other between layers, and an inner peripheral side of the sub belt And a belt including a main belt having a spiral winding structure of a cord extending substantially in the tread circumferential direction. One or more insert plies, which are made of a rubber coating layer of polyketone fiber and extend continuously from one tire side to the other tire side, are arranged between the turn-up ply and the down ply. It will be.

Here, all the polyketone fiber cords satisfy the following formulas (I) and (II).
α ≧ −0.01E + 1.2 (I)
α ≧ 0.02 (II)
[In the formula, α is a heat shrinkage stress (cN / dtex) at 177 ° C., and E is an elastic modulus (cN / dtex) at a load of 49 N at 25 ° C. ]

  By the way, this heat shrinkage stress α is obtained by heating a 25 cm long sample of a polyketone fiber cord before vulcanization subjected to a general dip treatment at a heating rate of 5 ° C./min. The stress generated in the cord at the time of measurement, and the elastic modulus E at 49 N load at 25 ° C. of the polyketone fiber cord is a unit cN / dtex calculated from the tangent at 49 N of the SS curve by the JIS cord tension test. Is the elastic modulus.

Since the polyketone fiber cord satisfying the above formulas (I) and (II) has a high breaking strength, when the cord is applied to a carcass ply, after satisfying the pressure resistance required for a pneumatic radial tire for aircraft, The number of carcass plies can be reduced as compared with the case where a nylon fiber cord is applied to a carcass ply, and a reduction in tire weight can be achieved.
In addition, polyketone fiber cords heat shrink with increasing temperature and have large heat shrinkability and fatigue resistance against compressive stress, so when cords made of aramid fibers are applied to carcass plies Prevents the occurrence of carcass ply sagging that occurs during tire manufacture or carcass ply breakage due to cord fatigue during running, and is equivalent to, or superior to, tires that use nylon fiber cords Can be secured.

  In order to make the present invention more effective, the heat shrinkage stress α is preferably 0.4 or more. However, if the heat shrinkage stress α is 1.5 or more, the shrinkage force during vulcanization is large. As a result, the cord in the tire and the rubber arrangement may be disturbed, resulting in deterioration of durability and uniformity.

Further, the height of the outer end in the radial direction of the winding part of the turn-up ply is measured from the rim diameter line under the tire posture that is assembled to the applicable rim and filled with the prescribed air pressure, and is the radius of the tire maximum width position. It is preferable to be in the range of 0.6 to 1.4 times the height in the direction.
That is, if it is less than 0.6 times, it is difficult to ensure sufficient rigidity of the bead portion. On the other hand, if it exceeds 1.4 times, the winding end is too close to the belt and separation occurs at the winding end. It becomes easy to do.

In this case, “applicable rim” refers to the rim specified in the following standards depending on the tire size, and “specified air pressure” refers to the air pressure specified in accordance with the maximum load capacity in the following standards. The maximum load capacity is the maximum mass allowed to be loaded on the tire according to the following standards.
The air here can be replaced with an inert gas such as nitrogen gas or the like.

  The standard is an industrial standard valid for the region where tires are produced or used. For example, “THE TIRE AND RIM ASSOCIATION INC. YEAR BOOK” in the United States, and “THE European Tire and Rim Technical” in Europe. “STANDARDS MANUAL of Organization”.

  In such a tire, the inner end of the insert ply in the radial direction is preferably positioned radially inward from the hoist end of the turn-up ply with the lowest radial height in the tire posture described above. Preferably, the insert ply is disposed adjacent to the outer side in the tire width direction of the turn-up ply of the turn-up ply having the lowest radial height of the roll-up portion.

  Here, the radially inner end portion of the insert ply is located at the winding portion of the turn-up ply having the lowest radial height of the winding portion. It is preferable to overlap within a range of ˜30 mm, in particular, 18 to 25 mm. On the other hand, the rubber thickness between cords between the insert ply and the turn-up ply wound portion adjacent to each other is 0. It is preferable to set it as the range of 5-3.0 mm, especially 0.8-2.8 mm.

In the pneumatic tire of the present invention, by configuring the radial carcass with a polyketone fiber cord having a high breaking strength, the pressure resistance performance comparable to that of the tire described in Patent Document 1, and the reduction in the number of carcass plies, In addition to reducing tire weight, for example, one or more turn-up plies can be replaced with insert plies that extend from one tire side to the other tire side to maintain pressure resistance performance. However, further weight reduction of the tire can be achieved.
That is, the insert ply here covers the entire region from the tire crown region to the tire side portion with low pressure resistance, so that weight reduction can be realized while ensuring high pressure resistance performance.
Thus, in this pneumatic tire, it is possible to exhibit excellent pressure resistance performance under high internal pressure conditions, and it is possible to realize further weight reduction.

  Here, when the radial inner end of the insert ply is positioned radially inward from the winding end of the turn-up ply with the lowest height in the radial direction and the smallest pull-out drag, the insert ply With this tensile strength, the pulling-out force of the turn-up ply is effectively countered and the pull-out can be effectively prevented.

  And this means that the insert ply is arranged adjacent to the outer side in the tire width direction of the turn-up ply of the turn-up ply having the lowest radial height of the hoist part and the smallest resistance against the pull-out force. In other words, the radial inner end portion of the insert ply is directly overlapped with the winding end portion of the turn-up ply, and the winding portion having the lowest radial height is covered with the insert ply. This is particularly effective when the pulling-out of the wound portion is constrained by the tensile strength of the adjacent insert ply.

By the way, the radially inner end portion of the insert ply is connected to the wound-up portion of the turn-up ply having the lowest radial height of the rolled-up portion in the extending direction of the insert ply of 15 to 30 mm, especially 18 to 25 mm. When overlapped within the range, the pull-out force acting on the winding portion can be more fully supported by the insert ply.
In other words, if the overlap amount is less than 15 mm, the pull-up of the winding portion can be sufficiently removed with the turn-up ply under the situation where the load tension per ply cord increases as the number of carcass plies decreases. While it becomes difficult to restrain, ply end separation due to the fact that both ply ends are too close tends to occur. On the other hand, if it exceeds 30 mm, the effect of reducing the weight of the insert ply is small. At the same time, the ride comfort is inevitably lowered with an increase in the rigidity of the tire side portion.

Moreover, the rubber thickness between cords including the cord covering rubber between the insert ply and the winding portion of the turn-up ply adjacent to each other is 0.5 to 3.0 mm, especially 0.8 to 2.8 mm. When it is in the range, it is possible to effectively relieve the shear stress generated in the rubber between cords by the force in the pulling-out direction of the winding portion, and to effectively remove the possibility of shear failure of the rubber between the cords.
In other words, if the rubber thickness is less than 0.5 mm, the inter-cord rubber may undergo shear deformation, and thus the shear stress becomes too large, and the inter-cord rubber may be sheared or broken from the cord. If it exceeds 3.0 mm, an increase in the weight of the tire cannot be denied, and the amount of heat generated increases, which may cause rubber blow inside.

FIG. 1 is a cross-sectional view in the width direction showing an embodiment of the present invention for a half portion of a tire. Here, the tire is assembled in an applied rim and shown in a posture filled with a prescribed air pressure.
In the figure, R denotes an applicable rim, 1 is a tread portion, 2 is a pair of sidewall portions continuous to each side portion of the tread portion 1, and 3 is an inner peripheral side of each sidewall portion 2. Each of the bead portions to be assembled to the bead sheet of the rim R is shown.
Here, each of the sidewall portion 2 and the bead portion 3 is collectively referred to as a tire side portion.

  In this tire, a plurality of, for example, five, made of a polyketone fiber cord rubber coating layer satisfying the above-described formulas (I) and (II) between a pair of bead cores 4 disposed in each bead portion 3. The carcass ply of each of the polyketone fiber cords is extended toroidal to form a radial carcass 5 in which each polyketone fiber cord extends at an angle in the range of 70 to 90 ° with respect to the tire equatorial plane E. For example, three sheets are used as turn-up plies 5a each side portion of which is wound around the bead core 4 from the inner side to the outer side in the tire width direction, and the remaining carcass plies are used as the turn-up ply 5a. A down ply 5b that includes the portion and extends at least to a radially inward position of the centroid of the bead core 4 is used.

  Further, here, on the outer peripheral side of the crown region of the radial carcass 5, for example, a secondary belt 6 b composed of two or more intersecting belt layers in which the cords intersect each other between the layers, and a cord in a linear or zigzag shape or the like A belt 6 constituted by one or more main belts 6a made of a spirally wound layer wound from one side of the auxiliary belt 6b toward the other side of the sub belt 6b; Further on the outer peripheral side of such a belt 6, a cut protector 7 in which a cord group in which a highly elastic cord is arranged in a wave shape with an amplitude S (2.0 ≦ S ≦ 20) is covered with rubber, and a tread rubber that partitions a tread surface 8 are arranged sequentially.

By the way, in such a tire, the radial outer end height H measured from the rim diameter line L of the winding portion 5c of each turn-up ply 5a is the same as the measured radial height at the tire maximum width position. Positioning within the range of 0.6 to 1.4 times H ₀ is suitable for preventing the separation at the winding end while securing the pull-out resistance of each winding portion 5c.

In such a tire, here, it extends continuously from one tire side part to the other tire side part between the turn-up ply 5a and the down ply 5b. ) And one insert ply 9 made of a rubber coating layer of polyketone fiber cord satisfying the above), for example, in order to reduce the number of turn-up plies 5a. Therefore, the pressure resistance of the entire region from the tire crown region to the tire side portion is prevented from being lowered.
Accordingly, the insert ply 9 here extends adjacent to the main body portion of the outermost turn-up ply 5a and the innermost down ply 5b.

  Here, the inner end in the radial direction of the insert ply 9 is positioned radially inward from the hoisting end of the turn-up ply 5a with the lowest height in the radial direction of the hoisting part 5c. This is preferable for exerting the pull-out restraining force.

  And preferably, as shown in the enlarged cross-sectional view of the main part in FIG. 2, the insert ply 9 has a turn-up ply 5a having the lowest radial height of the hoisting portion 5c, the outer side in the tire width direction of the hoisting portion 5c, As shown in the drawing, the innermost turn-up ply 5a is disposed adjacent to the outer side in the tire width direction of the winding portion 5c, and the protection against the winding portion having the smallest pull-out drag force is more effective.

  By the way, the radially inner end portion of the insert ply 9 is irrespective of whether or not the insert ply 9 is directly adjacent to the winding portion 5c of the turn-up ply having the lowest radial height of the winding portion 5c (see FIG. 2, the insert ply 9 is disposed adjacent to the winding portion 5 c having the lowest radial height), but the length within the range of 15 to 30 mm in the extending direction of the insert ply 9. It is preferable to make it overlap over the length d in order to effectively counteract the insert ply 9 by pulling out the minimum winding portion 5c.

Further, the inter-cord rubber thickness ga measured in the direction perpendicular to the winding portion 5c between the insert ply 9 and the winding portion 5c of the turn-up ply 5a adjacent to each other is 0.5-3. A range of 0 mm is preferable in order to relieve shear stress generated in the rubber between cords and to prevent shear fracture of the rubber between cords.
This also applies to the inter-cord rubber thickness gb measured in the direction orthogonal to the down ply 5b between the insert ply 9 and the innermost down ply 5b adjacent to each other.

  As described above, the embodiment has been described with reference to the illustrated embodiment, but the number of turn-up ply 5a, down ply 5b, and insert ply 9 can be changed as appropriate.

  When the tire weight, breaking pressure, and tire side portion durability of a radial aircraft tire having a size of 1400 × 530R23 40PR were measured for each of the example tire, the conventional tire, and the comparative tire, the results shown in Table 1 were obtained. It was.

Here, the breaking pressure is obtained by filling the tire with pressurized water, measuring the pressure at the time when the tire breaks, and evaluating the index using the conventional tire as a control,
The durability of the tire side is measured by measuring the temperature of the tire tread by filling the air pressure specified in the standard (1720 kPa in this tire), rolling the tire under the load specified in the standard. The number of times until separation occurred at the end of the insert ply was measured by a drum test that was intermittently repeated under the test conditions for determining the test interval, and was obtained by index evaluation using a conventional tire as a control.
The occurrence of separation at the insert ply end was confirmed by a shearography test.
By the way, it was assumed that the larger the index value, the better the result.
On the other hand, the smaller the index value of weight, the lighter the weight.

According to the results shown in Table 1, it can be understood that all of the tires of Examples can realize a reduction in tire weight while ensuring excellent pressure resistance performance.
The tires 2 and 4 of the examples have a feeling that the durability of the tire side portions cannot be denied due to the small amount of overlap between the insert ply and the winding up portion of the turn-up ply.

FIG. 3 is a cross-sectional view in the width direction showing a half portion of the tire in a tire posture in which a form of an embodiment of the present invention is assembled to an applicable rim and filled with a prescribed air pressure. It is sectional drawing which expands and shows the principal part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Radial carcass 5a Turn-up ply 5b Down ply 5c Winding part 6 Belt 6a Main belt 6b Sub belt 7 Cut protector 8 Tread rubber 9 Insert ply E Tire equatorial plane R Applicable rim L Rim diameter line d Overlap length ga, gb Rubber thickness between cords

Claims (5)

Each side portion is composed of a plurality of carcass plies formed of a rubber coating layer of a polyketone fiber cord extending in a toroidal manner between a pair of bead cores at an angle in a range of 70 to 90 ° with respect to the tire equatorial plane. A radial carcass including one or more turn-up plies wound around the bead core from the inner side to the outer side in the tire width direction and one or more down plies that enclose the wound part of the turn-up ply, and a radial carcass A pneumatic radial tire comprising a belt disposed on the outer peripheral side of the crown region of
A pneumatic radial comprising a rubber cover layer of polyketone fiber between the turn-up ply and the down ply, and one or more insert plies extending from one tire side to the other tire side. tire.   2. The pneumatic radial tire according to claim 1, wherein the radially inner end of the insert ply is positioned radially inward from the wound end of the turn-up ply that has the lowest raised portion in the radial direction.   The pneumatic radial tire according to claim 1 or 2, wherein the insert ply is disposed adjacent to the outer side in the tire width direction of the turn-up ply of the turn-up ply having the lowest radial height of the roll-up portion.   The radial end portion of the insert ply is overlapped within the range of 15 to 30 mm in the extending direction of the insert ply with the winding portion of the turn-up ply having the lowest radial height of the winding portion. The pneumatic radial tire according to any one of 1 to 3.   The pneumatic radial tire according to any one of claims 1 to 4, wherein the inter-cord rubber thickness between the insert ply and the turn-up ply wound portion adjacent to each other is in the range of 0.5 to 3.0 mm. .

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