JP2014108684A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which can reduce the weight and rolling resistance thereof and can improve separation resistance performance while satisfactorily maintaining steering stability.SOLUTION: In a pneumatic tire which installs two carcass layers 4 including a plurality of carcass cords between a pair of bead parts 3, 3, arranges a bead core 5 and a bead filler 6 in each of the bead parts 3, and arranges at least two belt layers 7 on the outer peripheral side of the carcass layer 4, both ends of the inner peripheral carcass layer 4A are folded back from the inside to the outside of the tire around the bead cores 5, both ends of the outer peripheral carcass layer 4B are arranged on the outside, in the width direction of the tire, of the folded back parts 4Ay of the inner peripheral carcass layer 4A and extended to positions overlapping at least the bead fillers 6, both ends of the outer peripheral carcass layer 4B are terminated at the bead parts 3 without being folded back around the bead cores 5, and auxiliary fillers 14 are disposed on the outside, in the width direction of the tire, of the outer peripheral carcass layer 4B so as to cover the terminals 4Be of the outer peripheral carcass layer 4B.

Description

  The present invention relates to a pneumatic tire having a plurality of carcass layers. More specifically, while maintaining good steering stability, the tire can be reduced in weight and rolling resistance can be reduced, and separation resistance can be improved. The present invention relates to a pneumatic tire that can be improved.

  In a pneumatic tire, in order to maintain a high internal pressure, a reinforcing structure in which a plurality of carcass layers are mounted between a pair of bead portions is employed. For example, a three-layer carcass layer is mounted between a pair of bead portions, and both end portions of two inner-circumference-side carcass layers are folded around the bead cores from the inside of the tire to the outside, while one outer-circular-side carcass layer is folded. There has been proposed a pneumatic tire having a so-called 2-1F ply-lock structure in which both end portions of the layer are arranged on the outer side in the tire width direction of the folded portion of the inner circumferential carcass layer (see, for example, Patent Document 1).

  FIG. 6 schematically shows a pneumatic tire having a conventional 2-1F ply lock structure. As shown in FIG. 6, both end portions of the inner peripheral side carcass layers 41, 42 are folded back from the inside of the tire around the bead core 5, and both end portions of the outer peripheral side carcass layer 43 are formed on the inner peripheral side carcass layers 41, 42. It is arrange | positioned outside the folding | returning part. In the pneumatic tire having such a 2-1F ply-lock structure, since the three carcass layers 41, 42, and 43 are present in the sidewall portion, good steering stability can be exhibited.

  However, since pneumatic tires are often exposed to harsh usage environments such as high load conditions caused by overloading and high internal pressure conditions to ensure load capacity, bending occurs in the bead part or sidewall part. If many terminals of the carcass layer are arranged at easy sites, separation failure starting from these terminals tends to occur. In addition, when three carcass layers are used, there is a problem that the tire weight increases, resulting in an increase in tire rolling resistance.

  Although the above-mentioned problem can be overcome by reducing the number of carcass layers, in this case, the rigidity of the entire tire is lowered, and steering stability is lowered.

Japanese Patent Laid-Open No. 11-32217

  An object of the present invention is to provide a pneumatic tire capable of reducing the tire weight and rolling resistance while improving steering stability while maintaining good steering stability. is there.

  In order to achieve the above object, the pneumatic tire of the present invention has two carcass layers including a plurality of carcass cords mounted between a pair of bead portions, and a bead core and a bead filler are disposed on each bead portion, In the pneumatic tire in which at least two belt layers are disposed on the outer peripheral side of the carcass layer, both end portions of the inner peripheral carcass layer are folded from the tire inner side to the outer side around each bead core, while both ends of the outer peripheral carcass layer are Extending at least to a position overlapping with the bead filler while disposing the portion on the outer side in the tire width direction than the folded portion of the inner circumferential carcass layer, and without folding both ends of the outer circumferential carcass layer around each bead core Auxiliary fillers are disposed so as to be terminated at each bead portion and to cover the end of the outer peripheral carcass layer on the outer side in the tire width direction than the outer peripheral carcass layer. And it is characterized in and.

  In the present invention, both end portions of the inner circumferential side carcass layer are folded around the respective bead cores from the inside to the outside of the tire, while both end portions of the outer circumferential side carcass layer are terminated at each bead portion without being folded around each bead core. Therefore, in the sidewall part, a three-layer structure consisting of the body part of the inner peripheral carcass layer and the folded part and the outer peripheral carcass layer is formed to sufficiently ensure the rigidity of the pneumatic tire, and exhibit good steering stability. can do. On the other hand, since only the two carcass layers are used as the skeleton structure of the tire and the surplus portion of the carcass layer is eliminated as much as possible, a pneumatic tire provided with three carcass layers as in the past In comparison with the above, the weight of the tire can be reduced, and the rolling resistance of the tire can be reduced.

  Further, according to the configuration of the present invention described above, there are two ends of the carcass layer on one side of the tire, and the ends of the folded portion of the inner peripheral carcass layer are the main body portion of the inner peripheral carcass layer and the outer peripheral carcass layer. Since the terminal of the outer peripheral side carcass layer is protected between the folded portion of the inner peripheral side carcass layer and the auxiliary filler, the separation failure starting from the terminal of the carcass layer is suppressed, and Separation performance can be improved.

  In the present invention, the end of the outer periphery side carcass layer is arranged on the outer side in the tire radial direction from the radially outermost end of the bead core, and the end of the outer periphery side carcass layer extends from the outermost end in the radial direction of the bead filler to the inner side in the tire radial direction. Disposed at a position that is 10 mm or more apart, arranged the radially outer end of the auxiliary filler on the outer side in the tire radial direction than the radially outermost end of the bead filler, and arranged the radially inner end of the auxiliary filler on the outer carcass layer end It is preferable to dispose the tire radially inward. While ensuring good separation resistance by ensuring sufficient overlap between the outer carcass layer and the bead filler, steering stability is sufficiently ensured by avoiding overlap between the outer carcass layer and the bead core. be able to. In addition, the auxiliary filler can be prevented from bending deformation of the bead filler by extending the outer side of the bead filler in the radial direction of the tire, and the auxiliary filler can be extended to the inner side of the outer side of the carcass layer in the radial direction of the tire. Therefore, separation resistance can be ensured.

  It is preferable that the auxiliary filler has a shape that gradually becomes thinner toward both sides in the tire radial direction, and the portion that becomes the maximum thickness of the auxiliary filler is disposed within a range where the bead filler and the auxiliary filler overlap. Thereby, the bending deformation of the bead filler can be effectively suppressed without increasing the weight excessively, and the durability can be improved.

  The bead filler, the auxiliary filler, and the sidewall rubber layer located on the outer side in the tire width direction than the auxiliary filler are composed of rubber compositions having different physical properties, and the auxiliary filler has a JIS hardness lower than that of the bead filler, And it is preferable to make JIS hardness of an auxiliary filler higher than JIS hardness of a sidewall rubber layer. By making the auxiliary filler harder than the sidewall rubber layer, it is possible to supplement the rigidity of the bead part and suppress separation failure starting from the end of the outer carcass layer, but the auxiliary filler's JIS hardness can be reduced. By lowering the JIS hardness of the filler, the rolling resistance can be reduced because the rigidity in the tire radial direction does not become higher than necessary.

  The loss tangent of the auxiliary filler at 60 ° C. is preferably 0.15 or less. Since the auxiliary filler is disposed at a position close to the rim flange, the rolling resistance can be reduced by making the auxiliary filler low heat generation.

  The terminal of the folded portion of the inner circumferential carcass layer is preferably disposed between the inner circumferential belt layer and the main body of the inner circumferential carcass layer. In this case, the rigidity of the side wall portion can be sufficiently ensured, and excellent steering stability can be exhibited, and the terminal portion of the folded portion of the inner circumferential carcass layer is connected to the inner circumferential belt layer and the inner circumferential side. Since it is located in a site | part with few distortions between carcass layers, the improvement effect of a separation resistance can be heightened.

  The overlap amount W between the folded portion of the inner circumferential side carcass layer and the inner circumferential side belt layer is preferably 5 mm to 40 mm. Thereby, a good separation resistance can be ensured.

  The breaking strength of the coat rubber of the inner circumferential carcass layer and the outer circumferential carcass layer is preferably 20 MPa or more. Thereby, the separation resistance can be improved.

  Moreover, it is preferable to arrange | position the buffer rubber layer whose breaking strength is 20 Mpa or more between each terminal of an outer peripheral side carcass layer and the folding | turning part of an inner peripheral side carcass layer. Thereby, the separation failure starting from each terminal of the outer peripheral side carcass layer can be suppressed, and the separation resistance can be improved.

  In the present invention, the outer peripheral side carcass layer can have a hollow structure divided in the lower region of the belt layer. In that case, the inner end in the tire width direction of each divided piece of the outer peripheral side carcass layer It is preferable to dispose at a position 5 mm or more away from the end of the folded portion of the carcass layer inward in the tire width direction. When the outer side carcass layer has a hollow structure in the lower region of the belt layer, it is possible to reduce the weight of the tire without causing a problem in tire performance, and the inner side in the tire width direction of each divided piece of the outer side carcass layer. Deterioration of the separation resistance can be avoided by optimizing the position of the terminal.

  In the present invention, JIS hardness is durometer hardness measured at a temperature of 20 ° C. using an A type durometer in accordance with JIS K-6253. The breaking strength is a tensile strength measured at a temperature of 20 ° C. using a dumbbell-shaped test piece in accordance with JIS K-6251. Loss tangent (tan δ) is measured in accordance with JIS-K6394 using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho) under the conditions of frequency 20 Hz, initial strain 10%, dynamic strain ± 2%, temperature 60 ° C. It is what is done.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. FIG. 2 is a meridian half sectional view schematically showing the pneumatic tire of FIG. 1. It is sectional drawing which expands and shows the bead part of the pneumatic tire of FIG. It is sectional drawing which shows roughly the modification of the bead part of the pneumatic tire of FIG. It is a meridian half sectional view schematically showing a pneumatic tire according to another embodiment of the present invention. It is a meridian cross-sectional view schematically showing a pneumatic tire having a conventional 2-1F ply lock structure.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 4 show a pneumatic tire according to an embodiment of the present invention.

  As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1, And a pair of bead portions 3 disposed inside the wall portion 2 in the tire radial direction.

  A pair of carcass layers 4 including a plurality of carcass cords extending in the tire radial direction is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes an inner circumferential carcass layer 4A located on the inner side in the tire radial direction in the tread portion 1 and an outer circumferential side carcass layer 4B located on the outer side in the tire radial direction in the tread portion 1. As the carcass cords constituting these carcass layers 4, organic fiber cords such as nylon and polyester are preferably used. An annular bead core 5 is embedded in each bead portion 3, and a bead filler 6 made of a rubber composition having a triangular cross section is disposed on the outer periphery of the bead core 5.

  On the other hand, at least two belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. The belt layer 7 includes an inner circumferential belt layer 7A located on the inner side in the tire radial direction and an outer circumferential side belt layer 7B located on the outer side in the tire radial direction. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7.

  On the outer peripheral side of the belt layer 7, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of 5 ° or less with respect to the tire circumferential direction is disposed for the purpose of improving high-speed durability. . It is desirable that the belt cover layer 8 has a jointless structure in which a strip material formed by aligning at least one reinforcing cord and covering with rubber is continuously wound in the tire circumferential direction. Further, the belt cover layer 8 may be disposed so as to cover the entire width direction of the belt layer 7, or may be disposed so as to cover only the outer edge portion of the belt layer 7 in the width direction. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In the pneumatic tire, both end portions of the inner circumferential carcass layer 4A are folded around the bead cores 5 from the inner side to the outer side so as to wrap the bead cores 5 and the bead fillers 6. The inner circumferential carcass layer 4A has a main body portion 4Ax inside the tire and a folded portion 4Ay outside the tire with the bead core 5 as a boundary. And terminal 4Ae of folding | turning part 4Ay of 4 A of inner periphery side carcass layers is arrange | positioned between 7 A of inner periphery side belt layers, and the main-body part 4Ax of 4 A of inner periphery side carcass layers. On the other hand, both end portions of the outer peripheral side carcass layer 4B are disposed on the outer side in the tire width direction with respect to the folded portion 4Ay of the inner peripheral side carcass layer 4A and extend at least to positions where they overlap with the bead filler 6, and both ends of the outer peripheral side carcass layer 4B. The portion terminates at each bead portion 3 without being folded around each bead core 5. That is, the terminal 4Be of the outer peripheral side carcass layer 4B is arranged in the vicinity of the bead core 5.

  In the pneumatic tire, a cap tread rubber layer 11 is disposed on the tread portion 1, a sidewall rubber layer 12 is disposed on the sidewall portion 2, and a rim cushion rubber layer 13 is disposed on the bead portion 3. However, the auxiliary filler 14 is disposed so as to cover the terminal 4Be of the outer peripheral carcass layer 4B at a portion on the inner side in the tire radial direction from the sidewall rubber layer 12 and on the outer side in the tire width direction from the outer peripheral carcass layer 4B. It is installed. The auxiliary filler 14 is harder than the sidewall rubber layer 12.

  In the pneumatic tire, both end portions of the inner circumferential carcass layer 4A are folded back from the inside of the tire around the respective bead cores 5 while the both end portions of the outer circumferential carcass layer 4B are folded back around the respective bead cores 5 without being folded back. Since the bead portion 3 is terminated, the sidewall portion 2 forms a three-layer structure including the main body portion 4Ax of the inner peripheral side carcass layer 4A, the turn-back portion 4Ay, and the outer peripheral side carcass layer 4B. Can be secured sufficiently, and good steering stability can be exhibited. In particular, since the terminal 4Ae of the folded portion 4Ay of the inner peripheral side carcass layer 4A is disposed between the inner peripheral side belt layer 7A and the inner peripheral side carcass layer 4A, sufficient rigidity of the sidewall portion 2 is ensured. be able to.

  On the other hand, since only the two carcass layers 4A and 4B are used as the skeleton structure of the tire and the surplus portion of the carcass layer 4 is eliminated as much as possible, the conventional carcass layer has three carcass layers. In comparison with a pneumatic tire, the weight of the tire can be reduced. In particular, since the folded portion 4Ay of the inner circumferential side carcass layer 4A extends to a position overlapping the inner circumferential side belt layer 7A, the side wall portion 2 has the three-layer structure of the carcass layer 4, while the tread portion 1 The carcass layer 4 can have a two-layer structure below the belt layer 7 in FIG. Moreover, since the both ends of the outer periphery side carcass layer 4B are not folded back around each bead core 5, the weight around the bead part 3 can be reduced. Thereby, a tire can be reduced in weight and rolling resistance of a tire can be reduced in connection with it.

  Furthermore, according to the pneumatic tire described above, there are two ends (4Ae, 4Be) of the carcass layer 4 on one side of the tire, and the end 4Ae of the folded portion 4Ay of the inner peripheral carcass layer 4A is the inner peripheral carcass layer 4A. Since the terminal portion 4Be of the outer peripheral side carcass layer 4B is protected between the folded portion 4Ay of the inner peripheral side carcass layer 4A and the auxiliary filler 14, the main body portion 4Ax and the outer peripheral side carcass layer 4B are protected. Separation failure starting from the terminal of the carcass layer 4 can be suppressed, and separation resistance can be improved. In particular, since the terminal 4Ae of the folded portion 4Ay of the inner peripheral side carcass layer 4A is located in a portion where there is little distortion between the inner peripheral side belt layer 7A and the inner peripheral side carcass layer 4A, the effect of improving the separation resistance is enhanced. be able to.

  As shown in FIG. 2, the overlap amount W between the folded portion 4Ay of the inner circumferential side carcass layer 4A and the inner circumferential side belt layer 7A is preferably 5 mm to 40 mm. Thereby, a good separation resistance can be ensured. When the overlap amount W is less than 5 mm, the terminal 4Ae of the inner peripheral side carcass layer 4A and the end of the inner peripheral side belt layer 7A are close to each other, so that the effect of improving the separation resistance is reduced. Since the usage amount of the layer 4 increases, the rolling resistance reduction effect is reduced. From the viewpoint of separation resistance, the overlap amount W is preferably 25 mm or more.

  Note that the overlap amount W is defined as the reference line of the inner peripheral side belt layer 7A and the outer side when the reference line passing through the terminal 4Ae of the inner peripheral side carcass layer 4A and orthogonal to the inner peripheral side belt layer 7A is obtained. The width of the part.

  As shown in FIG. 3, the terminal 4Be of the outer peripheral side carcass layer 4B is disposed on the outer side in the tire radial direction from the radially outermost end of the bead core 5, and the terminal 4Be of the outer peripheral side carcass layer 4B is the radial direction of the bead filler 6 It is arranged at a position 10 mm or more away from the outermost end inward in the tire radial direction. That is, the terminal 4Be of the outer periphery side carcass layer 4B is arranged in a region X defined between a radially outermost end of the bead core 5 and a position 10 mm inward in the tire radial direction from the radially outermost end of the bead filler 6. Has been. Thus, while ensuring good separation resistance by sufficiently ensuring the overlap between the outer peripheral side carcass layer 4B and the bead filler 6, it is controlled by avoiding the overlap between the outer peripheral side carcass layer 4B and the bead core 5. Sufficient stability can be ensured. When the terminal 4Be of the outer circumferential carcass layer 4B is located on the outer side in the tire radial direction from the region X, the terminal 4Be of the outer circumferential carcass layer 4B is close to the apex of the bead filler 6 and the separation resistance is degraded. When the end 4Be of the layer 4B is on the inner side in the tire radial direction from the region X and the end of the outer peripheral side carcass layer 4B is on the side of the bead core 5, the position of the bead core 5 when the tire is fitted to the wheel Is offset to the inner side in the tire width direction and a desired fitting force cannot be obtained, so that steering stability is lowered. Further, when the terminal 4Be of the outer periphery side carcass layer 4B is disposed in the region X, if the terminal 4Be is brought close to the apex of the bead filler 6, the resistance is reduced due to weight reduction, and if the terminal 4Be is brought close to the bead core 5, rigidity is obtained. The increase will lead to high steering stability. Furthermore, in consideration of durability, the end 4Be of the outer peripheral side carcass layer 4B may be separated from the rim flange contact portion.

  On the other hand, the radially outer end of the auxiliary filler 14 is disposed on the outer side in the tire radial direction with respect to the radially outermost end of the bead filler 6, and the radially inner end of the auxiliary filler 14 is more tired than the end 4Be of the outer-side carcass layer 4B. Arranged radially inside. Bending deformation of the bead filler 6 can be suppressed by extending the auxiliary filler 14 to the outer side in the tire radial direction than the bead filler 6, and the auxiliary filler 14 is arranged in the tire radial direction inner side than the terminal 4Be of the outer peripheral carcass layer 4B. Separation resistance performance can be ensured by extending the length to.

  The auxiliary filler 14 has a crescent-shaped cross-sectional shape that becomes gradually thinner toward both sides in the tire radial direction, and the portion that is the maximum thickness of the auxiliary filler 14 is preferably disposed within a range where the bead filler 6 and the auxiliary filler 14 overlap. . Thereby, the bending deformation of the bead filler 6 can be effectively suppressed without increasing the weight excessively, and the durability can be improved. In addition, when the cross-sectional shape of the auxiliary filler 14 is not a crescent moon shape and the thickness of the auxiliary filler 14 is constant along the tire radial direction, an excessive weight increase causes an increase in rolling resistance. For the same reason, the maximum thickness of the auxiliary filler 14 is preferably set to 6 mm or less.

  In the pneumatic tire, the bead filler 6, the auxiliary filler 14, and the sidewall rubber layer 12 located on the outer side in the tire width direction from the auxiliary filler 12 are made of rubber compositions having different physical properties. More specifically, the JIS hardness of the auxiliary filler 14 is set lower than the JIS hardness of the bead filler 6, and the JIS hardness of the auxiliary filler 14 is set higher than the JIS hardness of the sidewall rubber layer 12. In particular, the JIS hardness of the auxiliary filler 14 may be set lower by 5 points or more than the JIS hardness of the bead filler 6. By making the auxiliary filler 14 harder than the sidewall rubber layer 12, it is possible to supplement the rigidity of the bead portion 3 and to suppress a separation failure starting from the terminal 4Be of the outer circumferential carcass layer 4B. On the other hand, by making the JIS hardness of the auxiliary filler 14 lower than the JIS hardness of the bead filler 6, the rolling resistance can be reduced because the rigidity in the tire radial direction does not become higher than necessary. The bead filler 6 has a JIS hardness set in the range of 80 to 95, the auxiliary filler 14 has a JIS hardness set in the range of 75 to 90, and the sidewall rubber layer 12 has a JIS hardness set in the range of 40 to 60. It is preferable to do.

  The loss tangent at 60 ° C. of the auxiliary filler 14 is preferably 0.15 or less. Since the auxiliary filler 14 is disposed at a position close to the rim flange, the rolling resistance can be reduced by making the auxiliary filler 14 low heat generation. If the loss tangent at 60 ° C. of the auxiliary filler 14 is greater than 0.15, the above-described effects cannot be obtained. In FIG. 1, the rim cushion rubber layer 13 and the auxiliary filler 14 are provided separately. However, these two members can be integrally formed from the same material. Can be improved.

  As shown in FIG. 4, a buffer rubber layer 15 having a breaking strength of 20 MPa or more is preferably disposed between each terminal 4Be of the outer peripheral carcass layer 4B and the folded portion 4Ay of the inner peripheral carcass layer 4A. Thereby, the separation failure which makes each terminal 4Be of the outer peripheral side carcass layer 4B a starting point can be suppressed, and a separation-proof performance can be improved. When the breaking strength of the buffer rubber layer 15 is less than 20 MPa, the effect of improving the separation resistance is reduced. The breaking strength of the buffer rubber layer 15 is desirably 25 MPa or more. The thickness of the buffer rubber layer 15 is preferably set in the range of 0.5 mm to 2.0 mm.

  As another method, the breaking strength of the coat rubber of the inner circumferential carcass layer 4A and the outer circumferential carcass layer 4B can be 20 MPa or more. Also in this case, the separation resistance can be improved as described above. Of course, the breaking strength of the coated rubber of the carcass layers 4A and 4B is set to 20 MPa or more, and at the same time, the breaking strength is 20 MPa or more between each terminal 4Be of the outer circumferential carcass layer 4B and the folded portion 4Ay of the inner circumferential carcass layer 4A. A certain buffer rubber layer 15 may be inserted. In this case, this is equivalent to a structure in which the coat rubber in the vicinity of each terminal 4Be of the outer peripheral side carcass layer 4B is locally thicker than other portions.

  FIG. 5 shows a pneumatic tire according to another embodiment of the present invention. 5, the same components as those in FIGS. 1 to 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 5, in the present embodiment, the outer peripheral side carcass layer 4 </ b> B has a hollow structure divided in a lower region of the belt layer 7. In this case, when the tire width direction inner side terminal 4Be ′ of each divided piece 4B ′ of the outer peripheral side carcass layer 4B is arranged at a position spaced 5 mm or more inward in the tire width direction from the terminal 4Ae of the folded portion 4Ay of the inner peripheral side carcass layer 4A. good. That is, when the distance D from the terminal 4Ae of the folded portion 4Ay of the inner peripheral side carcass layer 4A to the tire width direction inner side terminal 4Be of the divided piece 4B ′ of the outer peripheral side carcass layer 4B toward the inner side in the tire width direction is set to 5 mm or more. good. When the outer peripheral side carcass layer 4B has a hollow structure in the lower region of the belt layer 7, there is no problem in tire performance, and the weight of the tire can be reduced. Here, the distance D is less than 5 mm, or the tire width direction inner side terminal 4Be ′ of each divided piece 4B ′ of the outer peripheral side carcass layer 4B is more tire than the terminal 4Ae of the folded portion 4Ay of the inner peripheral side carcass layer 4A. If it is located outside in the width direction, the separation resistance is deteriorated.

  In tire size 225 / 70R16, a plurality of carcass layers including a plurality of carcass cords are mounted between a pair of bead portions, a bead core and a bead filler are disposed in each bead portion, and two layers are provided on the outer peripheral side of the carcass layer. The tires of the conventional example, the comparative example 1, and the examples 1 to 7 in which the ply-lock structure of the carcass layer was varied in the pneumatic tire in which the belt layer was arranged.

  The conventional tire has a 2-1F ply-lock structure (see FIG. 6) using three carcass layers, and both end portions of the inner peripheral carcass layer (first ply and second ply) are connected to each bead core. On the other hand, both ends of the outer carcass layer (third ply) are arranged on the outer side of the inner carcass layer in the tire width direction while extending at least to a position overlapping with the bead filler. Both ends of the carcass layer are terminated at each bead portion without being folded around each bead core.

  The tire of Comparative Example 1 has a 1-1F ply-lock structure using two carcass layers, and both end portions of the inner circumferential carcass layer (first ply) are folded around each bead core so that the inner circumferential carcass While the end of the folded portion of the layer is disposed between the inner peripheral belt layer and the main body of the inner peripheral carcass layer, both end portions of the outer peripheral carcass layer (second ply) are folded around each bead core. The auxiliary filler is disposed so as to cover the end of the outer peripheral carcass layer on the outer side in the tire width direction than the outer peripheral carcass layer. In Comparative Example 1, both end portions of the outer peripheral side carcass layer are located on the outer side in the tire width direction with respect to the folded portion of the inner peripheral side carcass layer, but do not reach the bead filler.

  The tires of Examples 1 to 7 have a 1-1F ply lock structure (see FIGS. 1 to 5) using two carcass layers, and both end portions of the inner circumferential carcass layer (first ply) Folding around the bead core, the end of the folded portion of the inner circumferential carcass layer is disposed between the inner circumferential belt layer and the main body of the inner circumferential carcass layer, while the outer circumferential carcass layer (second ply) Both ends are arranged at the outer side in the tire width direction than the folded portion of the inner circumferential carcass layer and extend to at least a position overlapping with the bead filler, and each bead without folding the both ends of the outer circumferential carcass layer around each bead core. The auxiliary filler is disposed so as to cover the end of the outer peripheral side carcass layer on the outer side in the tire width direction than the outer peripheral side carcass layer.

  In particular, in the tires of Examples 6 and 7, a buffer rubber layer was disposed between each end of the outer peripheral carcass layer and the folded portion of the inner peripheral carcass layer. In the tire of Example 7, the outer peripheral side carcass layer has a hollow structure divided in the lower region of the belt layer, and the inner ends in the tire width direction of the divided pieces of the outer peripheral side carcass layer are the folded portions of the inner peripheral side carcass layer. It arrange | positioned in the position 20 mm away in the tire width direction inner side from the terminal.

  In the above-described conventional example, comparative example 1 and examples 1 to 7, the end position of the carcass layer (first to third plies) (the distance from the outermost end in the tire radial direction of the bead core) to the inner side Overlap amount W between the folded portion of the circumferential side carcass layer and the inner circumferential side belt layer, JIS hardness of the bead filler, JIS hardness of the auxiliary filler, JIS hardness of the sidewall rubber layer, loss tangent of the auxiliary filler at 60 ° C., carcass The breaking strength of the coated rubber and the breaking strength of the buffer rubber layer were set as shown in Table 1.

  These test tires were evaluated for tire weight, rolling resistance, steering stability, and separation resistance by the following evaluation methods, and the results are also shown in Table 1.

Tire weight:
The weight of each test tire was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. A larger index value means lighter weight.

Rolling resistance:
Each test tire is assembled to a wheel of rim size 16 × 6 1/2 JJ and mounted on a rolling resistance tester equipped with a drum having a radius of 854 mm, and the pressure is 210 kPa, the load is 6.47 kN, and the speed is 80 km / h for 30 minutes. After the preliminary running, the rolling resistance was measured under the same conditions. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. It means that rolling resistance is so small that this index value is large.

Steering stability:
Each test tire was assembled on a wheel with a rim size of 16 × 6 1/2 JJ and mounted on a test vehicle, and sensory evaluation was performed on a test course by a test driver under the condition of an air pressure of 210 kPa. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability.

Separation resistance:
Each test tire is assembled to a wheel with a rim size of 16 × 6 1/2 JJ and mounted on a drum durability tester. A running test is conducted under the conditions of air pressure 440 kPa, load 12.9 kN, speed 81 km / h, and separation of the carcass layer. The mileage until failure was measured. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the separation resistance.

  As can be seen from Table 1, in comparison with the conventional example, the tires of Examples 1 to 7 can reduce the weight of the tire and reduce the rolling resistance while maintaining good steering stability, and also have separation resistance. Was able to improve.

  On the other hand, in the tire of Comparative Example 1, since both end portions of the outer circumferential side carcass layer did not reach the bead filler, the steering stability was worse than that of the conventional example, and the separation resistance was also lowered.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 4A Inner circumference side carcass layer 4B Outer circumference side carcass layer 5 Bead core 6 Bead filler 7 Belt layer 7A Inner circumference side belt layer 7B Outer circumference side belt layer 8 Belt cover layer 11 Tread rubber Layer 12 Side wall rubber layer 13 Rim cushion rubber layer 14 Auxiliary filler 15 Buffer rubber layer

Claims (10)

  A two-layer carcass layer including a plurality of carcass cords is mounted between a pair of bead portions, a bead core and a bead filler are disposed on each bead portion, and at least two belt layers are disposed on the outer peripheral side of the carcass layer. In each of the pneumatic tires, both end portions of the inner circumferential carcass layer are folded around the bead cores from the inner side of the tire to the outer side, while both end portions of the outer circumferential carcass layer are wider than the folded portion of the inner circumferential carcass layer. The outer side carcass layer extends to a position overlapping at least the bead filler while being arranged on the outer side in the direction, and ends at each bead portion without being folded back around each bead core. A pneumatic tire characterized in that an auxiliary filler is disposed on the outer side in the width direction so as to cover the terminal of the outer peripheral side carcass layer.   The terminal of the outer periphery side carcass layer is disposed on the outer side in the tire radial direction with respect to the radially outermost end of the bead core, and the terminal of the outer periphery side carcass layer is disposed on the inner side in the tire radial direction from the outermost end in the radial direction of the bead filler. It arrange | positions in the position away from 10 mm or more, arrange | positions the radial direction outer side terminal of the said auxiliary filler in a tire radial direction outer side rather than the radial direction outermost end of the said bead filler, and arrange | positions the radial direction inner side terminal of the said auxiliary filler on the said outer peripheral side. The pneumatic tire according to claim 1, wherein the pneumatic tire is disposed on the inner side in the tire radial direction from the end of the carcass layer.   The auxiliary filler has a shape that gradually becomes thinner toward both sides in the tire radial direction, and the portion that is the maximum thickness of the auxiliary filler is disposed within a range where the bead filler and the auxiliary filler overlap. The pneumatic tire according to claim 1 or 2.   The bead filler, the auxiliary filler, and a sidewall rubber layer located on the outer side in the tire width direction than the auxiliary filler are composed of rubber compositions having different physical properties, and the JIS hardness of the auxiliary filler is based on the JIS hardness of the bead filler. The pneumatic tire according to any one of claims 1 to 3, wherein the JIS hardness of the auxiliary filler is made higher than that of the sidewall rubber layer.   The pneumatic tire according to any one of claims 1 to 4, wherein a loss tangent of the auxiliary filler at 60 ° C is 0.15 or less.   The pneumatic according to any one of claims 1 to 5, wherein a terminal of the folded portion of the inner peripheral side carcass layer is disposed between the inner peripheral side belt layer and the main body portion of the inner peripheral side carcass layer. tire.   The pneumatic tire according to claim 6, wherein an overlap amount W between the folded portion of the inner circumferential side carcass layer and the inner circumferential side belt layer is 5 mm to 40 mm.   The pneumatic tire according to any one of claims 1 to 7, wherein a breaking strength of a coat rubber of the inner peripheral carcass layer and the outer peripheral carcass layer is 20 MPa or more.   The buffer rubber layer having a breaking strength of 20 MPa or more is disposed between each terminal of the outer peripheral carcass layer and the folded portion of the inner peripheral carcass layer. Pneumatic tires.   The outer peripheral side carcass layer has a hollow structure divided in the lower region of the belt layer, and the inner end in the tire width direction of each divided piece of the outer peripheral side carcass layer extends from the end of the folded portion of the inner peripheral side carcass layer to the tire. The pneumatic tire according to any one of claims 1 to 9, wherein the pneumatic tire is disposed at a position 5 mm or more inward in the width direction.

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