JP2018192960A - Pneumatic bias tire - Google Patents

Abstract

To provide a pneumatic bias tire capable of improving durability performance without increasing the piece number of carcasses.SOLUTION: An objective pneumatic bias tire has a reinforcing rubber 12 at the outside of a fitting face with a rim in a tire radial direction and at a tire inner cavity side of a carcass layer nearest to a tire equator face. The reinforcing rubber 12 in a cross section in a tire meridian direction is at least provided between a first position being whichever in the range from a position of the outermost side in the tire radial direction of a bead filler 4c whose height in that direction is highest to a position of height of 0.9 time the flange height FH of the rim 30, and a second position being the tire radial position of a center point Pa in a bead core 3a of the innermost side nearest to the tire equator face.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic bias tire.

  In general, industrial vehicle tires are set to high pressure and high load. For example, a heavy load bias tire used for a gantry crane used in a harbor or the like has a high load setting and a high center of gravity. For this reason, such a bias tire is easily subjected to an uneven load, and vehicle wobbling or tire failure may occur due to excessive deflection. However, further high pressure setting is difficult due to wheel strength and operational management problems.

  By the way, patent document 1 discloses the technique which arrange | positions an auxiliary | assistant rubber layer in a bead heel part. The auxiliary rubber layer disclosed in Patent Document 1 has a substantially triangular cross section with a tapered tip at least from the lower end of the outermost bead core toward the upper end.

JP 2006-1111074 A

  In heavy-duty bias tires, the load on the carcass around the bead tends to increase with the improvement in torque due to recent vehicle evolution. In particular, in a WB (Wide Base) size bias tire having a low flatness ratio used under an overload condition, cord breakage or ply separation may occur. Cord broken up (hereinafter referred to as CBU) is a case in which the carcass ply comes into strong contact with the winding end of the steel wire of the bead core at the innermost point in the tire axial direction, leading to the breakage. CBU is generated by excessive pulling of beads and carcass on the innermost surface side in the tire width direction.

  The ply separation is a peeling failure between a bead filler and a carcass provided in contact with the bead filler. The ply separation occurs in the tire width direction due to distortion between the inner surface side carcass layer close to the tire equatorial plane and the outer surface side carcass layer far from the tire equatorial plane.

  As a general measure, an increase in the number of carcass can be considered so as to withstand excessive tension. However, this countermeasure leads to productivity deterioration, cost increase, and weight increase. The technique disclosed in Patent Literature 1 cannot prevent the occurrence of CBU due to excessive tensile stress being applied to the bead core carcass closest to the tire equatorial plane.

  The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic bias tire that can suppress the movement of the bead core and can improve durability without increasing the number of carcass. .

  In order to solve the above-described problems and achieve the object, a pneumatic bias tire according to an aspect of the present invention includes a plurality of pairs of bead cores, and a plurality of bead fillers provided corresponding to each of the plurality of pairs of bead cores. A plurality of carcass layers provided corresponding to each of the plurality of pairs of bead cores, wherein each of the plurality of bead fillers is disposed on an outer side in the tire radial direction of the plurality of pairs of bead cores. These are pneumatic bias tires that are wound and wrapped while wrapping the bead core and the bead filler, respectively, on the tire radial direction outer side from the fitting surface with the rim in which the pneumatic bias tire is incorporated. A reinforcing rubber provided closer to the tire lumen than the carcass layer closest to the equator plane; In the meridional section, among the plurality of bead fillers, the height of the rim flange is 0.9 times the height of the rim flange from the outermost position in the tire radial direction of the bead filler having the highest height in the tire radial direction. The position in the tire radial direction of the center point of the innermost bead core closest to the tire equatorial plane among the plurality of pairs of bead cores in the cross section in the tire meridian direction in the first position which is any position in the range up to the position of Between the second position and the second position.

  Further, in the cross section in the tire meridian direction, the position outside the tire width direction from the position on the straight line connecting the center point of the innermost bead core and the bead toe is the third position, and the reinforcing rubber is in the cross section in the tire meridian direction. At least from the first position through the second position to the third position may be provided continuously.

  In the cross section in the tire meridian direction, the position of the perpendicular line from the center point of the innermost bead core to the tire rotation axis is the fourth position, and the reinforcing rubber is at least from the first position in the cross section in the tire meridian direction. It may be provided continuously through the second position and the third position to the fourth position.

  In the cross section in the tire meridian direction, the fifth position is a position of a perpendicular line from the center point of the intermediate bead core next to the tire equatorial plane next to the innermost bead core to the tire rotation axis, and the reinforcing rubber is a cross section in the tire meridian direction. In this case, at least the first position, the second position, the third position, and the fourth position may be continuously provided to the fifth position.

  In the cross section in the tire meridian direction, among the plurality of bead fillers, the reinforcement along a straight line that passes through a position that is 1/2 the height in the tire radial direction of the bead filler closest to the tire equatorial plane and that is parallel to the tire rotation axis It is preferable that A / 3 ≦ B ≦ A, where B is the thickness of the rubber and A is the total thickness of the plurality of bead fillers along the straight line.

  It is preferable to further include another carcass layer surrounding the plurality of carcass layers.

  The carcass layer further includes at least one chafer, the reinforcing rubber is provided between the carcass layers and the chafer, and an end of the chafer is formed of the reinforcing rubber. It is preferable that it is located outside the tire radial direction from the position.

  The reinforcing rubber preferably has a 100% elongation modulus of 1.5 MPa or more.

  The winding carcass of each bead core is preferably 4 or more and 8 or less.

  The cord angle of the innermost carcass layer in the tire width direction is preferably 25 degrees or more and 45 degrees or less with respect to the tire circumferential direction.

  According to the pneumatic bias tire according to the present invention, the reinforcement rubber is arranged on the tire lumen side from the bead core closest to the tire equatorial plane, thereby suppressing the movement of the bead core and improving the durability performance without increasing the number of carcass. be able to.

FIG. 1 is a cross-sectional view in the meridian direction of a pneumatic bias tire according to this embodiment. FIG. 2 is an enlarged view showing a bead portion of the pneumatic bias tire of FIG. FIG. 3 is a diagram for explaining an example of a range in which reinforcing rubber is provided in a cross section in the tire meridian direction. FIG. 4 is a diagram for explaining an example of a range in which reinforcing rubber is provided in a cross section in the tire meridian direction. FIG. 5 is a diagram for explaining an example of a range in which reinforcing rubber is provided in a cross section in the tire meridian direction. FIG. 6 is a diagram for explaining an example of a range in which reinforcing rubber is provided in a cross section in the tire meridian direction. FIG. 7 is a diagram for explaining an example of the thickness of the reinforcing rubber. FIG. 8 is a diagram for explaining an example of the thickness of the reinforcing rubber in the case of further including another carcass layer that wraps a plurality of carcass layers.

  Hereinafter, an embodiment of a pneumatic bias tire according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. A plurality of modified examples described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art. In the following description of each drawing, the same or equivalent components as those in the other drawings are denoted by the same reference numerals, and the description thereof is simplified or omitted.

  A pneumatic bias tire according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view in the meridian direction of a pneumatic bias tire according to this embodiment. FIG. 1 shows a cross-sectional view in the tire radial direction. FIG. 1 shows a pneumatic bias tire for a vehicle or a loader used in a harbor or the like as an example of a pneumatic bias tire. FIG. 2 is an enlarged view showing a bead portion of the pneumatic bias tire of FIG. FIG. 2 shows the boundary line between the carcass layers omitted.

  In FIG. 1, the section in the tire meridian direction means a section when the tire is cut along a plane including a tire rotation axis (not shown). Reference sign CL denotes a tire equator plane, which is a plane that passes through the center point of the tire in the tire rotation axis direction and is perpendicular to the tire rotation axis. Further, the tire radial direction means a direction perpendicular to the tire rotation axis. The tire width direction refers to a direction parallel to the tire rotation axis, and the tire circumferential direction refers to a direction around the tire rotation axis.

  In FIG. 1, the pneumatic bias tire 1 of the present embodiment has an annular structure centered on the tire rotation axis. The pneumatic bias tire 1 (hereinafter, appropriately referred to as the bias tire 1) has bead cores 3a, 3b, and 3c embedded in plural (three in FIG. 1) in a pair of left and right bead portions 2 and 2, respectively. The bias tire 1 has bead fillers 4a, 4b, and 4c corresponding to the bead cores 3a, 3b, and 3c. The bias tire 1 has carcass layers 10a, 10b, and 10c corresponding to the bead cores 3a, 3b, and 3c.

  In FIG. 1, the prescribed rim is indicated by a broken line. The bias tire 1 shown in FIG. 1 shows a shape in a state where the rim is not assembled. When the bias tire 1 is assembled to the rim 30, the end surfaces of the bead portions 2, 2 on the inner side in the tire radial direction are in contact with the fitting surface of the rim 30. At this time, the position of the bead toe 50 is on the outer side in the tire radial direction from the position shown in the figure, and is the position of the rim 30. The bead toe 50 is an end portion of the bead portions 2 and 2 that is closest to the tire equatorial plane.

  The specified rim refers to an “applied rim” defined in JATMA, a “Design Rim” defined in TRA, or a “Measuring Rim” defined in ETRTO. The specified internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The specified load means the “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  The pair of bead cores 3a, 3b, and 3c is an annular member formed by bundling a plurality of bead wires, and constitutes the core of the left and right bead portions. The bead fillers 4a, 4b, and 4c are rubber materials that are disposed on the outer side in the tire radial direction of the pair of bead cores 3a, 3b, and 3c. The bead fillers 4a, 4b, and 4c constitute a bead portion together with the pair of bead cores 3a, 3b, and 3c. In the cross section in the tire meridian direction, the thickness of the bead fillers 4a, 4b, and 4c in the tire width direction gradually decreases from the position of the corresponding bead cores 3a, 3b, and 3c toward the outer side in the tire radial direction. By gradually reducing the rigidity of the bead fillers 4a, 4b, and 4c toward the outer side in the tire radial direction, concentration of distortion when the bias tire 1 is bent is prevented, and CBU and carcass ply separation due to local distortion concentration are prevented. Can be prevented.

  The bias tire 1 includes a plurality of carcass layers 10a, 10b, and 10c in which the cord directions intersect with each other on each bead core 3a, 3b, and 3c. The carcass layers 10a, 10b, and 10c are wound up from the inner side to the outer side in the tire width direction so that the cord directions intersect with each other between adjacent pairs. Each of the carcass layers 10a, 10b, and 10c is bridged between a pair of bead cores. At the same time, the end portions of the carcass layers 10a, 10b, 10c are wound and locked while wrapping the bead cores 3a, 3b, 3c and the corresponding bead fillers 4a, 4b, 4c.

  The number of carcasses included in each of the carcass layers 10a, 10b, and 10c is preferably 4 or more and 8 or less. If the number of carcasses included in each of the carcass layers 10a, 10b, and 10c is less than 4 in a high-load and high-torque vehicle, it is not sufficient to support the bead, and if the number of carcasses exceeds 8, the bias tire 1 Since the workability at the time of molding is significantly impaired, it is not preferable.

  The carcass plies of the carcass layers 10a, 10b, and 10c are formed by rolling a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with a coat rubber. . As the carcass plies of the carcass layers 10a, 10b, and 10c, a plurality of the same ones may be used, or different ones may be mixed. For example, one outermost carcass ply of the plurality of carcass plies to be wound may have a different vulcanization degree from other carcass plies. Thus, the bias tire 1 has two or more carcass layers.

  The tread rubber 15 is disposed on the outer circumference in the tire radial direction of the carcass layers 10a, 10b, and 10c and the belts 8 and 8a to constitute the tread portion 5 of the tire. The pair of sidewall rubbers 17, 17 are arranged on the outer sides in the tire width direction of the carcass layers 10 a, 10 b, 10 c to constitute the left and right sidewall portions 7. The pair of rim cushion rubbers 20 and 20 are respectively disposed on the inner side in the tire radial direction of the rewind portions of the left and right bead cores 3a, 3b, and 3c and the carcass layers 10a, 10b, and 10c. 2 contact surfaces are formed. The bias tire 1 may not have the rim cushion rubber 20 in some cases.

  The bias tire 1 has a groove 11 in the tread portion 5. In FIG. 1, the groove bottom of the groove 11 is indicated by a broken line. Both ends of the tread portion 5 in the tire width direction are formed as shoulder portions 6, and sidewall portions 7 are disposed from the shoulder portions 6 to predetermined positions inside the tire radial direction. The sidewall portions 7 are disposed at two places on both sides of the bias tire 1 in the tire width direction. The sidewall portions 7 and 7 have a pair of sidewall rubbers 17 and 17.

  Furthermore, the bias tire 1 has belts 8 and 8a that are fiber reinforcement layers on the outer peripheral side of the carcass layer 10c in the tread portion 5. An inner liner 9 is formed along the carcass layer 10 a on the inner side of the bias tire 1.

  Further, the bias tire 1 has chafers 13a and 13b that wrap the entire carcass layers 10a, 10b, and 10c in the bead portion 2. In this example, a chafer 13b is provided outside the chafer 13a. The bias tire 1 does not need to have two chafers 13a and 13b, and may have at least one chafer. The reinforcing rubber 12 is provided between the plurality of carcass layers 10a, 10b, and 10c and the chafers 13a and 13b. The ends Ta and Tb of the chafers 13a and 13b are located on the outer side in the tire radial direction from the position of the reinforcing rubber 12. As a result, the rigidity of the bead cores 3a, 3b, 3c, the carcass layers 10a, 10b, 10c and the reinforcing rubber 12 can be gradually lowered. By gradually lowering the rigidity, it is possible to suppress an increase in shear strain and increase the fixing degree of the bead cores 3a, 3b, and 3c while maintaining the durability. Further, by sandwiching the chafers 13a and 13b between the contact surfaces of the bias tire 1 and the rim 30, it is possible to prevent the rubber from being scraped by contact between the rim 30 and the rubber constituting the bead portion 2.

[Reinforced rubber]
The bias tire 1 has a reinforcing rubber 12 in the bead portion 2. As shown in FIG. 2, the reinforcing rubber 12 is provided closer to the tire lumen than the carcass layer 10a closest to the tire equatorial plane CL on the outer side in the tire radial direction from the fitting surface with the rim into which the bias tire 1 is assembled. The reinforcing rubber 12 has a cross section in the tire meridian direction from the outermost position H1 in the tire radial direction of the bead filler 4c having the highest height in the tire radial direction among the plurality of bead fillers 4a, 4b, 4c. A plurality of pairs in a cross section in the tire meridian direction with any position (hereinafter referred to as a first position) in a range up to a position 0.9 times as high as the flange height FH (FH × 0.9). Of the bead cores 3a, 3b and 3c, a position H2 (hereinafter referred to as a second position) in the tire radial direction of a center point Pa of the innermost bead core (hereinafter referred to as the innermost bead core as appropriate) 3a closest to the tire equatorial plane CL. At least). That is, referring to FIG. 2, one end T1 of the reinforcing rubber 12 is within the range from the position H1 to a position 0.9 times as high as the flange height FH of the rim 30 (FH × 0.9). Is located. Referring to FIG. 2, the other end T2 of the reinforcing rubber 12 is located within a range from the position H2 to a straight line S1 connecting the center point Pa and the bead toe 50. Since the tension is particularly strong on the outer side in the tire radial direction from the separation point of the flange 30F of the rim 30, the reinforcing rubber 12 is extended up to 0.9 times the height of the flange 30F of the rim 30 that is the position of separation from the rim 30. It is necessary to exist. In addition, when the reinforcing rubber 12 is extended from the bead filler 4c to the upper side in the tire radial direction, the rigidity becomes stronger only on the tire lumen side than the bead filler 4c. As a result, the shear strain increases, the durability performance decreases, and ply separation is likely to occur.

[Physical properties such as reinforced rubber]
The reinforcing rubber 12 preferably has a 100% elongation modulus of 1.5 MPa or more. If the 100% elongation modulus is lower than this, a sufficient bead fixing effect cannot be expected. Further, the 100% elongation modulus of the reinforcing rubber 12 is preferably 2.5 MPa or less. If it is harder than this, the distortion due to the difference in hardness with the surrounding members increases, and the durability performance deteriorates.

  The reinforcing rubber 12 preferably has a breaking elongation of 500% or more and 600% or less. The reinforcing rubber 12 preferably has a tan δ at 60 ° C. of 0.02 or more and 0.08 or less. Further, the reinforcing rubber 12 preferably has a rubber hardness indicated by JIS-A hardness of 49 or more and 53 or less. 100% elongation modulus and elongation at break are determined according to JIS-K6251, tan δ is determined according to JIS-K6394, and JIS-A hardness is determined according to JIS-K6253.

  The rim cushion rubber 20 preferably has a 100% elongation modulus of, for example, not less than 1.8 MPa and not more than 2.2 MPa. The rim cushion rubber 20 preferably has an elongation at break of, for example, 560% or more and 650% or less. The rim cushion rubber 20 preferably has a tan δ at 60 ° C. of, for example, 0.11 or more and 0.17 or less. Further, the rim cushion rubber 20 preferably has a rubber hardness indicated by JIS-A hardness of, for example, 53 or more and 57 or less.

  The bead fillers 4a, 4b, 4c preferably have a 100% elongation modulus of, for example, 5.2 MPa or more and 5.6 MPa or less. The bead fillers 4a, 4b, and 4c preferably have an elongation at break of, for example, 250% or more and 350% or less. The bead fillers 4a, 4b, and 4c preferably have a tan δ at 60 ° C. of, for example, 0.16 or more and 0.22 or less. Furthermore, the bead fillers 4a, 4b, and 4c preferably have a rubber hardness indicated by JIS-A hardness of, for example, 67 or more and 71 or less.

[Reinforcing rubber installation range]
The bias tire 1 may have a reinforcing rubber in a wider range than the range shown in FIG. 2 in the cross section in the tire meridian direction. FIG. 3 to FIG. 6 are diagrams illustrating examples of ranges in which reinforcing rubber is provided in the cross section in the tire meridian direction.

  For example, as shown in FIG. 3, in the cross section in the tire meridian direction, when the position outside the tire width direction from the position on the straight line S1 connecting the center point Pa of the innermost bead core 3a and the bead toe 50 is the third position. In addition, the bias tire 1 may include a reinforcing rubber 12a that is continuously provided from the first position to the third position through the second position in the cross section in the tire meridian direction. That is, referring to FIG. 3, one end T1 of the reinforcing rubber 12a is within a range from a position H1 to a position 0.9 times as high as the flange height FH of the rim 30 (FH × 0.9). Is located. Referring to FIG. 3, the other end T3 of the reinforcing rubber 12a is located within a range from the straight line S1 to the position of the vertical line Sa extending from the center point Pa of the innermost bead core 3a to the tire rotation axis J. ing. By providing the reinforcing rubber 12a at this position, the movement of the innermost bead core 3a is suppressed, which is effective for the CBU of the carcass.

  Further, for example, as shown in FIG. 4, when the position of the vertical line Sa dropped from the center point Pa of the innermost bead core 3 a to the tire rotation axis J in the cross section in the tire meridian direction is the fourth position, the bias tire 1 May have a reinforcing rubber 12b continuously provided from the first position to the fourth position through the second position and the third position in the cross section in the tire meridian direction. That is, referring to FIG. 4, one end T1 of the reinforcing rubber 12b is within a range from a position H1 to a position 0.9 times as high as the flange height FH of the rim 30 (FH × 0.9). Is located. Referring to FIG. 4, the other end T4 of the reinforcing rubber 12b is located at the center of a bead core 3b (hereinafter referred to as an intermediate bead core) that is closest to the tire equatorial plane CL next to the innermost bead core 3a from the position of the perpendicular line Sa. It is located within the range from the point Pb to the position of the perpendicular line Sb drawn down to the tire rotation axis J.

  Further, for example, as shown in FIG. 5, in the cross section in the tire meridian direction, when the position of the perpendicular Sb dropped from the center point Pb of the intermediate bead core 3 b to the tire rotation axis J is the fifth position, the bias tire 1 is In the cross section in the tire meridian direction, the reinforcing rubber 12c may be provided continuously from at least the first position to the fifth position through the second position, the third position, and the fourth position. That is, referring to FIG. 5, one end T1 of the reinforcing rubber 12c is within a range from a position H1 to a position 0.9 times as high as the flange height FH of the rim 30 (FH × 0.9). Is located. Referring to FIG. 5, the other end T5 of the reinforcing rubber 12c is lowered from the position of the perpendicular Sb to the tire rotation axis J from the center point Pc of the bead core 3c next to the tire equatorial plane CL next to the intermediate bead core 3b. It is located within the range up to the position of the vertical line Sc. By providing the reinforcing rubber 12c at this position, the connection between the innermost bead core 3a and the outer bead core 3b becomes strong, and excessive movement of the bead core alone can be suppressed.

  Similarly, the bias tire 1 may have a reinforcing rubber (not shown) provided at least continuously from the first position to a position on the outer side in the tire width direction from the position of the perpendicular line Sc.

  FIG. 6 shows an enlarged view of a bead portion further including another carcass layer covering a plurality of carcass layers. As illustrated in FIG. 6, the bias tire 1 may further include another carcass layer 100 that covers the plurality of carcass layers 10 a, 10 b, and 10 c corresponding to the plurality of pairs of bead cores 3 a, 3 b, and 3 c. In this example, the carcass layer 100 has a so-called turn-down structure that terminates at the inner side in the tire radial direction of the bead portion 2 without winding up the end portion. In this example, a reinforcing rubber 12 c is provided between the plurality of carcass layers 10 a, 10 b, 10 c and the other carcass layer 100. But the reinforcement rubber | gum 12c may be provided in the tire radial direction inner side of the other carcass layer 100 which covers several carcass layers 10a, 10b, 10c.

  Note that the end portion of the carcass layer 100 may be rolled up, and the carcass layers 100a, 10b, and 10c may be entirely wrapped and terminated. Further, the end portion of the carcass layer 100 may be terminated on the side of the bead core 3c, that is, on the outer side in the tire width direction. The number of carcasses included in the carcass layer 100 is preferably 4 or more and 8 or less. The carcass ply of the carcass layer 100 is formed by rolling a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon) with a coat rubber. A plurality of the same carcass plies of the carcass layer 100 may be used, or different ones may be mixed.

[Reinforcing rubber thickness]
FIG. 7 is a diagram for explaining an example of the thickness of the reinforcing rubber. Referring to FIG. 7, one end T1 ′ of the reinforcing rubber 12d is within a range from a position H1 to a position 0.9 times as high as the flange height FH of the rim 30 (FH × 0.9). positioned. Referring to FIG. 7, the other end T5 of the reinforcing rubber 12d is located within a range from the position of the vertical line Sb to the position of the vertical line Sc.

Here, in FIG. 7, among the plurality of bead fillers 4a, 4b, and 4c, the bead filler 4a closest to the tire equatorial plane CL passes through a position (H3 / 2) that is 1/2 the height H3 in the tire radial direction. The thickness of the reinforcing rubber 12d along the straight line S2 parallel to the tire rotation axis J is B. Also, let A be the sum of the thicknesses A1, A2, and A3 of the plurality of bead fillers 4a, 4b, and 4c along the straight line S2. In this case, it is desirable that the reinforcing rubber 12d satisfies the formula (1).
A / 3 ≦ B ≦ A (1)

  If the reinforcing rubber 12d is thicker than the height H3 at the half position (H3 / 2), the rigidity on the tire lumen side becomes stronger than the bead filler 4a. As a result, the shear strain increases, the durability performance decreases, and ply separation is likely to occur. For this reason, it is preferable to satisfy | fill Formula (1). About the inside in the tire radial direction from the position of the bead filler 4a, the thickness of the reinforcing rubber 12d does not have to satisfy the formula (1). For this reason, as shown in FIG. 7, for example, the thickness of the reinforcing rubber 12d may be thicker than in the case of FIG. 5 at the second position (position H2) and the position on the straight line S1. The thickness of the reinforcing rubber 12d shown in FIG. 7 is the thickest in the vicinity of the position on the straight line S1.

  FIG. 8 is a diagram for explaining an example of the thickness of the reinforcing rubber in the case of further including another carcass layer 100 that wraps the plurality of carcass layers 10a, 10b, and 10c. Also in the case shown in FIG. 8, it is desirable that the reinforcing rubber 12d satisfies A / 3 ≦ B ≦ A as described with reference to FIG.

[Operation at high load]
In FIG. 7, during a high load, the bias tire 1 is subjected to a stress in a direction indicated by an arrow Y <b> 1 by a force acting in the tire width direction and a force acting outward in the tire radial direction. If the bias tire 1 does not have the reinforcing rubber 12d, if the rigidity on the inner surface side from the bead toe 50 is insufficient with respect to the load, the bead toe 50 may be lifted from the rim 30 and excessive distortion may occur. When excessive distortion occurs in this way, CBU is generated in the carcass layer 10a corresponding to the bead core 3a, or separation is generated in the rubber near the carcass layer 10a. On the other hand, the bias tire 1 of the present embodiment has a reinforcing rubber 12d, and the reinforcing rubber 12d is provided between the first position and the second position. For this reason, the rigidity on the inner surface side from the bead toe 50 can be sufficiently secured, and the occurrence of CBU and separation can be prevented. The configuration of FIG. 8 is the same as the above-described action, and the rigidity on the inner surface side from the bead toe 50 can be sufficiently secured, and the occurrence of CBU and separation can be prevented. 2 to 5 is the same as the above-described operation, and the rigidity on the inner surface side from the bead toe 50 can be sufficiently secured, and the occurrence of CBU and separation can be prevented.

[Summary]
In order to prevent CBU and separation due to excessive tension on the inner surface side carcass layer closest to the tire equator plane, an increase in the number of carcass is conceivable as a general measure to withstand excessive tension. However, this countermeasure leads to productivity deterioration, cost increase, and weight increase. According to the bias tire of the present embodiment, the reinforcement rubber is disposed closer to the tire lumen than the bead core closest to the tire equatorial plane, thereby suppressing the movement of the bead core and improving the durability performance without increasing the number of carcass. it can.

  Durability performance was evaluated about the bead part 2 of the bias tire 1 of this embodiment. In this example, a tire of 29.5-25 L22 size is mounted on a specified rim, the vehicle is run under a 650 kPa (TRA standard: 350 kPa), 150% load condition, and a failure occurs in the bead part 2. Durability performance was evaluated by running time.

  Further, as a conventional example, a tire not having a reinforcing rubber and not having a chafer was prepared. Furthermore, as a comparative example, it has a reinforced rubber, one end of the reinforced rubber is located outside the range of the first position, the other end of the reinforced rubber reaches the second position, A tire having no chafer with a 100% elongation modulus of the reinforcing rubber being 1.3 MPa and a thickness B of the reinforcing rubber being less than the lower limit of the formula (1) was prepared.

  As shown in Tables 1 and 2, the bias tires of Examples 1 to 15 have reinforcing rubber. In the bias tires of Examples 1 to 15, one end portion of the reinforcing rubber is located within the range of the first position. In the bias tires of Examples 1 to 15, the other end of the reinforcing rubber is continuously provided up to the second position, up to the third position, up to the fourth position, and up to the fifth position. Tire. The bias tires of Examples 1 to 15 were bias tires having a 100% elongation modulus of the reinforcing rubber of 1.3 MPa, 1.5 MPa, 2.0 MPa, and 2.5 MPa. The bias tires of Examples 1 to 15 were bias tires in which the thickness B of the reinforcing rubber was less than the lower limit value, the lower limit value, the intermediate value, and the upper limit value of Equation (1). The bias tires of Example 1 to Example 15 were prepared with a chafer and those without a chafer. Further, as for the bias tire having a chafer, a tire having a positional relationship in which reinforcing rubber is provided on the outside of the chafer and a tire having a positional relationship in which reinforcing rubber is provided between the carcass layer and the chafer are prepared. In the bias tires of Examples 1 to 15, a reinforcing rubber having a breaking elongation of 545%, a tan δ at 60 ° C. of 0.05, and a rubber hardness of 51 shown by JIS-A hardness was used. In the bias tires of Examples 1 to 15, the rim cushion rubber is a rubber having a 100% elongation modulus of 2.0 MPa, a breaking elongation of 605%, a tan δ at 60 ° C. of 0.14, and a JIS-A hardness. A hardness of 55 was used. In the bias tires of Examples 1 to 15, the bead filler has a 100% elongation modulus of 5.4, an elongation at break of 300%, an tan δ at 60 ° C. of 0.19, and an JIS-A hardness. A rubber hardness of 69 was used.

  In the conventional example, the comparative example, and the examples 1 to 15, the number of the carcass plies constituting each of the carcass layers 10a, 10b, 10c, and 100 is set to a number of 4 to 8, and the most in the tire width direction. The angle of the cord of the inner carcass layer was set to 25 degrees or more and 45 degrees or less with respect to the tire circumferential direction.

  According to Table 1 and Table 2, when one end of the reinforcing rubber is located within the range of the first position and the other end of the reinforcing rubber continues to the second position, when it continues to the third position, In either case of continuous to the fourth position or continuous to the fifth position, better results were obtained than in the case of the conventional example and the comparative example. Further, according to Tables 1 and 2, when the 100% elongation modulus of the reinforcing rubber is 1.5 MPa or more and 2.5 MPa or less, good results are obtained when the thickness B of the reinforcing rubber satisfies the formula (1). It was. Further, according to Tables 1 and 2, good results are obtained when the chafer is provided, and the reinforcing rubber is more easily attached to the carcass layer and the chafer than when the reinforcing rubber is provided outside the chafer. Good results were obtained when it was provided in between.

DESCRIPTION OF SYMBOLS 1 Pneumatic bias tire 2 Bead part 3a, 3b, 3c Bead core 4a, 4b, 4c Bead filler 5 Tread part 6 Shoulder part 7 Side wall part 8, 8a Belt 9 Inner liner 10a, 10b, 10c, 100 Carcass layer 11 Groove 12 12a, 12b, 12c, 12d Reinforcing rubber 13a, 13b Chafer 15 Tread rubber 17 Side wall rubber 20 Rim cushion rubber 30 Rim 30F Flange 50 Bead toe

Claims (10)

A plurality of bead cores; a plurality of bead fillers provided corresponding to each of the plurality of pairs of bead cores; and a plurality of carcass layers provided corresponding to each of the plurality of pairs of bead cores; Each of the fillers is a pneumatic bias tire that is disposed outside the plurality of pairs of bead cores in the tire radial direction, and each of the plurality of carcass layers is wound and wrapped around the bead core and the bead filler. There,
A reinforcing rubber provided on the tire lumen side of the carcass layer closest to the tire equatorial plane on the outer side in the tire radial direction from the fitting surface with the rim into which the pneumatic bias tire is incorporated;
In the cross section in the tire meridian direction, the reinforcing rubber has a height of 0 rim flange height from the outermost position in the tire radial direction of the bead filler having the highest height in the tire radial direction among the plurality of bead fillers. The center point of the innermost bead core closest to the tire equatorial plane among the plurality of pairs of bead cores in the cross section in the tire meridian direction in the first position that is any position in the range up to a position 9 times the height A pneumatic bias tire provided at least between the second position which is a position in the tire radial direction. In the cross section in the tire meridian direction, the third position is a position on the outer side in the tire width direction from a position on a straight line connecting the center point of the innermost bead core and the bead toe,
2. The pneumatic bias tire according to claim 1, wherein the reinforcing rubber is continuously provided at least from the first position through the second position to the third position in a cross section in the tire meridian direction. In the cross section in the tire meridian direction, the position of the perpendicular drawn from the center point of the innermost bead core to the tire rotation axis is the fourth position,
The pneumatic rubber according to claim 2, wherein the reinforcing rubber is continuously provided from the first position through the second position and the third position to the fourth position in a cross section in the tire meridian direction. Bias tire. In the cross section in the tire meridian direction, the position of the perpendicular drawn from the center point of the intermediate bead core next to the tire equatorial plane next to the innermost bead core to the tire rotation axis is the fifth position,
The reinforcing rubber is continuously provided at least from the first position to the fifth position through the second position, the third position, and the fourth position in a cross section in the tire meridian direction. The pneumatic bias tire described in 1. In the section in the tire meridian direction,
Among the plurality of bead fillers, the thickness of the reinforcing rubber along a straight line that passes through a position that is 1/2 the height in the tire radial direction of the bead filler closest to the tire equatorial plane is defined as B, When the sum of the thicknesses of the plurality of bead fillers along the straight line is A,
A / 3 ≦ B ≦ A
The pneumatic bias tire according to any one of claims 1 to 4.   The pneumatic bias tire according to any one of claims 1 to 5, further including another carcass layer that wraps the plurality of carcass layers. Further comprising at least one chafer enclosing the entire carcass layer;
The said reinforcement rubber is provided between the said carcass layer and the said chafer, The edge part of the said chafer is located in the tire radial direction outer side from the position of the said reinforcement rubber, Any of Claim 1-6 The pneumatic bias tire according to claim 1.   The pneumatic bias tire according to any one of claims 1 to 7, wherein a 100% elongation modulus of the reinforcing rubber is 1.5 MPa or more.   The pneumatic bias tire according to any one of claims 1 to 8, wherein the winding carcass of each of the bead cores is 4 or more and 8 or less.   The pneumatic bias tire according to any one of claims 1 to 9, wherein the cord angle of the innermost carcass layer in the tire width direction is 25 degrees or greater and 45 degrees or less with respect to the tire circumferential direction.