JP2007161003A - Radial tire for aircraft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radial tire for an aircraft capable of considerably enhancing the durability by providing an adequate belt structure. <P>SOLUTION: The tire 1 has a carcass layer 6 consisting of a pair of right and left bead parts 3, 3 with a bead core 2 embedded therein, a pair of side wall parts 4, 4, and a carcass ply extending in a toroidal manner to each portion of a tread part 5, main belt layers 7a-7d arranged between a crown area of the carcass layer and the tread part 5 while a ribbon-shaped member with an organic fiber cord covered with a rubber is spirally wound in the tire circumferential direction, and sub belt layers 8a, 8b arranged between the main belt layers and the tread part 5 with a nylon fiber cord covered with a rubber. In the main belt layers 7a-7d, the thickness T<SB>1</SB>of an interlayer rubber in both end areas 9 outside the width position of 80% of the maximum width BW of the main belt layers around the tire equatorial plane CL is larger than the thickness T<SB>2</SB>of the interlayer rubber at the position of the tire equatorial plane CL. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention extends in a toroidal manner across a pair of left and right bead portions in which bead cores are embedded, a pair of sidewall portions extending outward in the tire radial direction from both bead portions, and a tread portion extending across both sidewall portions. A carcass layer composed of at least one carcass ply, and a ribbon-like member that is disposed between a crown region and a tread portion of the carcass layer and covered with a rubber-coated organic fiber cord is configured by spirally winding in the tire circumferential direction. Further, the present invention relates to a radial tire for an aircraft having a plurality of main belt layers and at least one sub belt layer disposed between the main belt layer and the tread portion and coated with a nylon fiber cord. The durability of the belt layer of the tire is improved.

  Since radial aircraft tires are used under severe conditions such as high internal pressure, high load, and high speed rotation, the protrusion of the tread portion in the radial direction is particularly likely to increase. When the tread portion protrudes in the radial direction, the tread rubber is stretched in the tire circumferential direction accordingly. If the foreign matter is stepped on in a state where the tread rubber is stretched in this way, there is a problem that the stepped foreign matter easily enters the tread portion and the belt layer is easily damaged. Also, the tire shoulder area wears faster than the center area due to the difference in diameter caused by the protruding amount in the center area in the tire width direction being larger than that at both end areas in the tire width direction and the drag phenomenon of the rotating tire. As a result, there is a problem of causing a phenomenon of shortening the life of the tire, that is, a so-called uneven wear phenomenon. Therefore, in the radial tire for aircraft, it is particularly required to suppress the protrusion of the tread portion.

  In addition, the radial tire for aircraft has a large number of belt layers in order to satisfy the required durability, and a large centrifugal force acts when rolling to cause further protrusion of the tread portion. There is also a demand.

  For example, Patent Document 1 discloses a highly rigid organic material such as an aromatic polyamide for the purpose of suppressing the radial growth of the tread portion and improving the durability against cut scratches due to foreign matters, and at the same time achieving a reduction in weight. An aircraft radial tire is described in which a main belt layer is formed using a fiber cord, and a sub belt layer is formed on the outer side in the tire radial direction using a low elastic organic fiber cord such as a nylon fiber.

International Publication No. 03/061991 Pamphlet

  By providing the sub belt layer as described in Patent Document 1, it is possible to prevent foreign matter from entering the main belt layer and to suppress the progress of cut flaws. However, since the low elastic organic fiber cords constituting such a sub belt layer are also generally heat-shrinkable, the cord interval of the main belt layer is reduced due to the shrinkage of the sub belt layer and the rubber flow during vulcanization molding. There are cases where the strain of the belt layer increases. Such an increase in strain can be an obstacle to improving belt durability as the aircraft becomes very large and demands for further enhancement of load capacity increase.

  An object of the present invention is to solve such problems of the prior art, and the object of the present invention is to provide an aircraft radial whose durability has been greatly improved by optimizing the belt structure. To provide tires.

  To achieve the above object, the present invention provides a pair of left and right bead portions in which bead cores are embedded, a pair of sidewall portions extending outward in the tire radial direction from both bead portions, and a tread extending over both sidewall portions. A carcass layer composed of at least one carcass ply extending in a toroidal shape over each part of the part, and a ribbon-like member that is disposed between the crown region of the carcass layer and the tread part and is covered with a rubber-coated organic fiber cord. An aircraft having a plurality of main belt layers spirally wound in a direction, and at least one sub-belt layer disposed between the main belt layer and the tread portion and made of rubber-coated nylon fiber cords In a radial tire, in the cross section in the tire width direction, the main belt layer is 80% of the maximum width of the main belt layer centering on the tire equatorial plane. The main belt layer is divided into two end regions outside the width position and a central region sandwiched between the two end regions, and the thickness of the interlayer rubber in the end region is the thickness of the interlayer rubber at the tire equatorial plane position. It is a radial tire for aircraft characterized by being larger than this. By adopting such a configuration, it is possible to ensure the thickness of the interlayer rubber at the end portion of the main belt layer where separation failure is likely to occur even when the sub belt layer is thermally contracted.

  The “thickness of the interlayer rubber” here refers to the thickness in the tire radial direction of the covering rubber (interlayer rubber) existing between the two cords constituting the two adjacent main belt layers. And between the two cords adjacent in the tire radial direction between the outermost end in the tire radial direction of the cord located on the inner side in the tire radial direction and the innermost end in the tire radial direction of the cord located on the outer side in the tire radial direction. This corresponds to the distance measured along the tire radial direction.

  Moreover, it is preferable that the thickness of the interlayer rubber in the end region of the main belt layer increases toward the outer side in the tire width direction.

  Furthermore, it is preferable that a rubber sheet is disposed between adjacent ribbon-like members.

  Furthermore, the maximum thickness of the interlayer rubber in the end region of the main belt layer is preferably in the range of 1.5 to 3.0 times the thickness of the interlayer rubber at the tire equatorial plane position.

  In addition, the tire width direction cord interval in the end region of the main belt layer is preferably in the range of 1.5 to 3.0 times the tire width direction cord interval in the center region. When the code interval changes in the end region and / or the central region, the average value of the code intervals in these regions satisfies the above condition.

  The maximum width of the main belt layer is preferably in the range of 90 to 120% of the tread width.

  Further, the sub-belt layer is configured such that a ribbon-like member formed by covering the cord with rubber is bent in the same plane so as to be inclined in the opposite direction at the width end portion, and extends in the tire circumferential direction in a zigzag manner. It is preferable to become.

  According to the present invention, the belt structure is optimized, and even when the secondary belt layer is thermally shrunk, particularly by ensuring the thickness of the interlayer rubber at the end of the main belt layer where the separation failure is likely to occur, It is possible to provide a radial tire for an aircraft with significantly improved performance.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view in the tire width direction of a typical aircraft radial tire (hereinafter referred to as “tire”) according to the present invention, and FIG. 2 is a cord in the right half region of the main belt layer of the tire shown in FIG. It is the schematic of arrangement | positioning.

  A tire 1 shown in FIG. 1 includes a pair of left and right bead portions 3, 3 in which a bead core 2 is embedded, a pair of sidewall portions 4, 4 extending from both bead portions 3, 3 outward in the tire radial direction, and both sidewall portions. 4 and 4 having a tread portion 5 extending over. In the tire 1, a carcass layer 6 composed of at least one carcass ply extending in a toroid shape over the bead portion 3, the sidewall portion 4, and the tread portion 5, and disposed between the crown region of the carcass layer 6 and the tread portion. In FIG. 1, four main belt layers 7a, 7b, 7c, 7d, and at least one sub belt layer disposed between the main belt layer and the tread portion, Two sub-belt layers 8a and 8b are embedded.

  The main belt layers 7a to 7d are so-called spiral belts formed by spirally winding a ribbon-like member formed by covering an organic fiber cord with rubber in a tire circumferential direction. By adopting a spiral belt applied to the main belt layer, it is possible to eliminate the polymerization of the sheet-like member at the joint portions at both ends in the circumferential direction, which has been inevitably generated when the belt layer is configured from the conventional sheet-like member, It is possible to eliminate unevenness in joint strength due to non-uniform joint dimensions of joints and steps in joints, and to suppress radial growth by the main belt layer. It has improved. From the viewpoint of enhancing the effect without significantly increasing the tire mass, the organic fiber cord constituting the ribbon-like member is a non-extensible and highly elastic, for example, aromatic polyamide fiber, particularly an aramid. It is preferable to use fibers. Here, “non-extensible” means that the elongation when a load of 0.3 cN / dtex is applied in the longitudinal direction is 2.0% or less, and “high elasticity” means The tensile strength at break is 6.3 cN / dtex or more.

  Nylon fiber cords are used as the cords constituting the auxiliary belt layers 8a and 8b. Nylon fiber cords have a relatively low elastic modulus, so even if the tire steps on foreign matter on the road surface and penetrates the tread portion and reaches the sub belt layer, the tension load factor of the sub belt layer cord is It is smaller than the cord of the main belt layer, and its influence on the tire radial direction growth suppressing effect is small. Moreover, since the stress concentration around the bottom of the cut flaw is reduced, there is an effect that the possibility of damage progressing is reduced even if the vehicle continues to run.

However, nylon fibers have a relatively high heat shrinkage rate. For this reason, at the time of vulcanization molding, the sub belt layer contracts due to heat, which tightens the main belt layer and causes a rubber flow between the main belt layers, resulting in a decrease in the thickness of the interlayer rubber of the product tire. If the thickness of the interlayer rubber is reduced, contact between adjacent cords is likely to occur, which may cause a decrease in tire durability. This tendency is particularly remarkable in the end regions 9 and 9 outside the width position of 80% of the maximum width BW of the main belt layers 7a to 7b with the tire equatorial plane CL as the center. Therefore, in the present invention, as shown in FIG. 2, the thickness of the interlayer rubber in the end region 9 of the main belt layer 7, that is, the tire radial direction code gap T between the two cords 10 and 10 adjacent in the tire radial direction. ₁ is made larger than the thickness T ₂ of the interlayer rubber on the tire equator surface, so that even if the secondary belt layer is thermally contracted during vulcanization molding, the cords are prevented from coming into contact with each other, and the durability of the tire is improved. It is improving. Further, by increasing the thickness of the interlayer rubber only in the end region as described above, the durability is maintained at the same level as compared with the case where the thickness of the interlayer rubber of the entire main belt layer 7 is uniformly increased. However, a significant weight reduction can be achieved.

The thickness T ₁ of the interlayer rubber in the end region 9 may be constant as shown in FIG. 2, but the rubber flow becomes larger toward the width end of the main belt layer, so that it is shown in FIG. thereby to increase the thickness T ₁ of the interlayer rubber in the end region 9 toward the outer side in the tire width direction such that prevents contact of the code cross, which is advantageous in improving the durability of the main belt layer. Incidentally, the thickness T ₁ in FIG. 3 shows an embodiment in which monotonically increases toward the outer side in the tire width direction, as shown in FIG. 4, it may be increased stepwise.

It means for increasing the thickness T ₁ of the interlayer rubber in the end region 9 is not particularly limited, for example in an end region 9 and the central region 11, but can also be used having different thicknesses ribbon-like member of the coating rubber It is particularly preferable to sandwich a rubber sheet between the ribbon-like members because the manufacturing process is relatively simple and the joined portion of the ribbon-like member does not increase.

Further, the maximum thickness T _max of the interlayer rubber in the end region 9 of the main belt layer 7 is set within a range of 1.5 to 3.0 times the thickness T ₂ of the interlayer rubber at the position of the tire equatorial plane CL. It is preferable. This is because if T _max / T ₂ is less than 1.5, it may be difficult to suppress an increase in the shear strain of the interlayer rubber. This is because the heat generation amount increases with the rubber amount, and there is a concern about deterioration of the main belt layer due to heat.

FIG. 5 is a schematic view of the cord arrangement in the right half region of the main belt layer 7 of another typical tire of the present invention. As illustrated, the tire width direction cord interval p ₁ in the end region 9 of the main belt layer 7 is preferably larger than the tire width direction cord interval p ₂ in the central region 11. This is because the main belt layer is forcibly deformed into a flat shape under the contact surface and is compressed in both end regions during rolling with tire load, but can be deformed in a direction in which the cord interval in both end regions becomes smaller. This is because the shearing force generated at the cord interface can be relaxed, the main belt layer can be smoothly deformed, and the local strain generated on the outer surface of the tread can be alleviated. More _preferably, the p 1 / _{p 2} in the range of 1.5 to 3.0. This is because if p ₁ / p ₂ is less than 1.5, the effect of suppressing the increase in distortion by securing the cord interval is not sufficient, and if it exceeds 3.0, the belt rigidity in the both end regions decreases. This is because the diameter growth of the shoulder portion of the tire increases, which may adversely affect durability and wear resistance. FIG. 5 shows a case where the code intervals in the both end regions and the central region are constant, but these may be changed. In this case, the average value of the code intervals in the both end regions is calculated. It is preferably 1.5 to 3.0 times the average value of the cord interval in the central region, and it is more preferable to gradually increase the cord interval toward the outer side in the tire width direction.

  Furthermore, the maximum width BW of the main belt layer 7 is preferably in the range of 90 to 120% of the tread width TW. This is because when the BW / TW is less than 90%, the effect due to the main belt layer is insufficient, and there is a possibility that the radial growth of the tread portion may not be sufficiently suppressed. This is because the mass increases and the requirement for weight reduction may not be satisfied.

  The auxiliary belt layers 8a and 8b can be formed by winding a wide sheet-like member once in the tire circumferential direction and joining the both ends thereof as in the case of a normal tire belt layer, as shown in FIG. Further, the ribbon-like member 12 formed by covering the cord with rubber is bent in the same plane so as to be inclined in the opposite directions at the width end portions 13a and 13b, respectively, so as to extend in the tire circumferential direction in a zigzag shape as a whole. It is preferable to configure. As a result, the auxiliary belt layers 8a and 8b have a configuration in which the width end portions 13a and 13b do not have the cut ends of the cords, so that it is possible to effectively prevent the occurrence of separation due to the rigidity step at the cord cut ends. This is because the durability of the belt layer can be improved.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. .

  Next, tires according to the present invention were prototyped and performance evaluations were performed, which will be described below.

  The tires of Examples 1 and 2 are radial tires for aircraft having a size of 1400 × 530R23 40PR, and have an overall structure as shown in FIG. 1, and the main belt layer uses an aramid fiber cord as shown in FIG. 2 (Example 1). ) And FIG. 5 (Example 2), and the auxiliary belt layer is formed by bending a ribbon-like member in a zigzag shape as shown in FIG. Have

  For comparison, the tire size is the same as in Examples 1 and 2, the overall structure as shown in FIG. 1, the aramid fiber cord is used for the main belt layer, and the auxiliary belt layer is as shown in FIG. Although the ribbon-like member is bent in a zigzag shape, the thickness of the interlayer rubber and the cord interval in the both end regions are the same as the thickness of the interlayer rubber and the cord interval in the central region, respectively. A tire of a conventional example having the specifications shown was also made on a trial basis.

  Each of the above test tires is assembled into a MEASURING RIM defined by TRA standards to form a tire wheel, and a belt in which tread swelling occurs by alternately repeating running for 4 minutes and stopping for 60 minutes on a drum testing machine under the following conditions. The cumulative mileage until the failure occurred was measured, and the durability was evaluated based on this measured value. The evaluation results are shown in Table 1. In addition, the durability evaluation results in Table 1 are shown as index ratios when the evaluation result of the conventional example is 100, and the larger the value, the higher the durability.

Test conditions-Test internal pressure: 90% of the normal internal pressure specified by TRA
・ Test load: 95% of the normal load specified in TRA
Test speed: 40 MPH (64 km / h)

  From the results shown in Table 1, it can be seen that the tires of Examples 1 and 2 have significantly improved belt durability as compared with the conventional tires. Further, from the comparison between the tire of Example 1 and the tire of Example 2, the durability is further increased by making the tire width direction cord interval of the both end regions of the main belt layer larger than the tire width direction cord interval of the central region. It turns out that it improves.

  As is apparent from the above description, according to the present invention, it is possible to provide a radial tire for an aircraft having a significantly improved durability.

1 is a cross-sectional view in the tire width direction of a typical radial aircraft tire according to the present invention. It is the schematic of the cord arrangement of the right half area of the main belt layer of the typical radial tire for aircrafts according to this invention. It is the schematic of the cord arrangement | positioning of the right half area of the main belt layer of the radial tire for other aircraft according to this invention. It is the schematic of the cord arrangement | positioning of the right half area of the main belt layer of the radial tire for other aircraft according to this invention. It is the schematic of the cord arrangement | positioning of the right half area of the main belt layer of the radial tire for other aircraft according to this invention. It is a top view of the subbelt layer of the representative radial tire for aircrafts according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Bead core 3 Bead part 4 Side wall part 5 Tread part 6 Carcass layer 7a, 7b, 7c, 7d Main belt layer 8a, 8b Sub belt layer 9 End area of main belt layer 10 Code 11 Central area of main belt layer 12 Ribbon-shaped members 13a, 13b Width end of the sub belt layer

Claims (7)

A pair of left and right bead portions with embedded bead cores, a pair of sidewall portions extending outward in the tire radial direction from both bead portions, and at least one piece extending in a toroidal shape over each portion of the tread portion extending over both sidewall portions. A carcass layer composed of a carcass ply, and a plurality of layers formed by spirally winding a ribbon-like member, which is disposed between a crown region and a tread portion of the carcass layer and covered with an organic fiber cord, in the tire circumferential direction. In an aircraft radial tire having a main belt layer, and at least one sub belt layer disposed between the main belt layer and the tread portion and rubber-coated with a nylon fiber cord,
In the cross-section in the tire width direction, the main belt layer is composed of both end regions outside the width position of 80% of the maximum width of the main belt layer centered on the tire equatorial plane, and a central region sandwiched between the both end regions. In the radial tire for aircraft, the main belt layer is characterized in that the thickness of the interlayer rubber in the end region is larger than the thickness of the interlayer rubber at the tire equatorial plane position.   The radial tire for an aircraft according to claim 1, wherein the thickness of the interlayer rubber in the end region of the main belt layer increases toward the outer side in the tire width direction.   The radial tire for aircraft according to claim 1, wherein a rubber sheet is disposed between adjacent ribbon-like members.   The maximum thickness of the interlayer rubber in the end region of the main belt layer is in the range of 1.5 to 3.0 times the thickness of the interlayer rubber at the tire equatorial plane position. Radial tire for aircraft as described in the paragraph.   5. The tire width direction cord interval in the end region of the main belt layer is in a range of 1.5 to 3.0 times the tire width direction cord interval in the center region. Radial tires for aircraft.   The radial tire for aircraft according to any one of claims 1 to 5, wherein a maximum width of the main belt layer is in a range of 90 to 120% of a tread width.   The sub-belt layer is formed by bending a ribbon-like member made of rubber-coated cords in the same plane so as to incline in opposite directions at the width ends, and extending in the tire circumferential direction in a zigzag manner. The radial tire for aircraft according to any one of claims 1 to 6.

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