JP6119230B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving bead crack resistance.

  FIG. 11 is an explanatory view showing a bead portion of a conventional pneumatic tire. The figure shows a state of a fitting portion between the bead portion and the rim 10 in the inflated state of the conventional pneumatic tire 100.

  As shown in FIG. 11, a general pneumatic tire 100 is attached to the rim 10 with a bead portion fitted to a rim flange portion 101. For this reason, the rim cushion rubber 117 is strongly pressed against the rim flange portion 101 in the inflated state, so that it greatly extends along the rim flange portion 101. Further, when the tire rolls, the rim cushion rubber 117 is deformed by an external force from the tire contact surface and repeatedly receives a compressive stress. For this reason, the conventional pneumatic tire 100 has a problem that the rim cushion rubber 117 is easily cracked.

  As conventional pneumatic tires related to such problems, techniques described in Patent Documents 1 and 2 are known.

JP 2008-273247 A JP 2008-285068 A

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can improve bead crack-proof performance.

In order to achieve the above object, a pneumatic tire according to the present invention includes a pair of bead cores, a carcass layer that spans between the pair of bead cores, and a rim flange portion that is disposed on the inner side in the tire radial direction of the carcass layer. A pneumatic tire comprising a pair of rim cushion rubbers that respectively constitute mating surfaces of bead portions, an intermediate rubber layer disposed between the rim cushion rubber and the carcass layer, and the rim cushion rubber; e Bei and a buffer rubber layer disposed on the outer side in the tire radial direction relative to the intermediate rubber layer a between the carcass layer, the modulus M1 of the intermediate rubber layer, and the modulus M0 of the rim cushion rubber , have a relationship M0 <M1, the modulus M2 of the buffer rubber layer, a 2.0 [MPa] ≦ M2 ≦ 4.0 [MPa], the slow Elongation at break B2 of the rubber layer is 400 [%] ≦ B2, and the rubber hardness of the cushion rubber layer H2 is characterized in that it is a 52 ≦ H2 ≦ 64.

  In the pneumatic tire according to the present invention, an intermediate rubber layer having a higher modulus than the rim cushion rubber is disposed between the rim cushion rubber and the carcass layer. Then, when the compressive stress is repeatedly applied to the rim fitting portion of the bead portion during rolling of the tire, the intermediate rubber layer functions as a buffer member and reduces the movement of the rim cushion rubber. Thereby, generation | occurrence | production of the crack in rim cushion rubber | gum is suppressed and there exists an advantage which the bead crack-proof performance of a tire improves.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a bead portion of the pneumatic tire shown in FIG. 1. FIG. 3 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 2. FIG. 4 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. FIG. 5 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 2. FIG. 6 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 2. FIG. 7 is an explanatory view showing a modified example of the pneumatic tire depicted in FIG. 2. FIG. 8 is an explanatory diagram showing a modification of the pneumatic tire depicted in FIG. FIG. 9 is an explanatory view showing a modification of the pneumatic tire shown in FIG. FIG. 10 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 11 is an explanatory view showing a bead portion of a conventional pneumatic tire.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. This figure shows one side region of a sectional view in the tire radial direction. The figure shows a radial tire mounted on a commercial light truck as an example of a pneumatic tire. In the figure, the symbol CL is the tire equator plane. The tire width direction means a direction parallel to a tire rotation axis (not shown), and the tire radial direction means a direction perpendicular to the tire rotation axis.

  The pneumatic tire 1 has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, and a tread rubber 15. And a pair of sidewall rubbers 16 and 16 and a pair of rim cushion rubbers 17 and 17 (see FIG. 1).

  The pair of bead cores 11 and 11 is an annular member formed by bundling a plurality of bead wires, and constitutes the core of the left and right bead portions. The pair of bead fillers 12 and 12 includes a lower filler 121 and an upper filler 122, which are disposed on the tire radial direction outer periphery of the pair of bead cores 11 and 11, respectively, to reinforce the bead portion.

  The carcass layer 13 is bridged in a toroidal shape between the left and right bead cores 11 and 11 to form a tire skeleton. Further, both ends of the carcass layer 13 are wound and locked from the inner side in the tire width direction to the outer side in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, nylon, polyester, rayon, etc.) with a coating rubber and rolling them, and has an absolute value of 85 [deg] or more and 95. [Deg] The following carcass angle (inclination angle in the fiber direction of the carcass cord with respect to the tire circumferential direction). In the configuration of FIG. 1, the carcass layer 13 has a single-layer structure composed of a single carcass ply. However, the present invention is not limited to this, and the carcass layer 13 has a multilayer structure formed by laminating a plurality of carcass plies. Also good.

  The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144, and is arranged around the outer periphery of the carcass layer 13. These belt plies 141 to 144 include, for example, a high-angle belt 141, a pair of cross belts 142 and 143, and a belt cover 144. Each belt ply 141 to 144 is formed by rolling a plurality of belt cords made of steel or organic fiber material coated with a coat rubber, and has a predetermined belt angle (inclination of the belt cord in the fiber direction with respect to the tire circumferential direction). Corner).

  The tread rubber 15 is disposed on the outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute a tread portion of the tire. The pair of side wall rubbers 16 and 16 are respectively arranged on the outer side in the tire width direction of the carcass layer 13 to constitute left and right side wall portions. The pair of rim cushion rubbers 17, 17 are respectively arranged on the inner side in the tire radial direction of the wound portions of the left and right bead cores 11, 11 and the carcass layer 13, and the fitting surfaces of the left and right bead portions with respect to the rim flange portion (not shown). Configure.

  In the configuration of FIG. 1, the pneumatic tire 1 includes three circumferential main grooves 21 and 22 extending in the tire circumferential direction, and four rows of land portions 31 that are partitioned by these circumferential main grooves. , 32 are provided in the tread portion.

[Rainforce]
The pneumatic tire 1 includes a reinforcement 20.

  The reinforcement 20 is a reinforcing layer made of a steel cord or an organic fiber cord, and is arranged from the sidewall portion to the bead portion and extends in the tire circumferential direction. The reinforcement 20 may be configured by, for example, covering a plurality of steel cords with a coat rubber and rolling them, or may be configured by winding a steel cord around a core to be spirally wound. In addition, the reinforcement 20 may be configured by rolling a plurality of nylon cords. This reinforcement 20 reinforces the rigidity of the bead portion and the sidewall portion, thereby improving the durability and steering stability of the tire.

  For example, in the configuration of FIG. 1, two layers of laminated reinforcements 20 and 20 are arranged on the left and right sides of the tire, respectively. Further, the reinforcement 20 is disposed so as to wrap around the winding portion of the carcass layer 13 and extends along the winding portion of the carcass layer 13 from a position inside the tire core in the tire width direction of the bead core 11. Is covered from the outside in the tire width direction. In addition, the reinforcement 20 is disposed in a region radially inward of the tire maximum width position, and is disposed along the bead filler 12 over the entire circumference of the tire.

  The reinforcement 20 is not an essential component and may be omitted (see FIG. 6 described later). Further, the reinforcement 20 may extend outward in the tire radial direction from the tire maximum width position.

[Intermediate rubber layer]
For example, in the Chinese market, a pneumatic tire may be used while being filled with a high air pressure of 1100 [kPa] to 1300 [kPa]. In such a use mode, the rim cushion rubber 117 is strongly pressed against the rim flange portion 110 in the inflated state. For this reason, the rim flange portion 110 bites into the rim cushion rubber 117, and the rim cushion rubber 117 greatly extends along the rim flange portion 110 (see FIG. 11). Further, when the tire rolls, the rim cushion rubber 117 is deformed by an external force from the tire contact surface and repeatedly receives a compressive stress. For this reason, there is a problem that cracks are likely to occur in the rim cushion rubber 117.

  Therefore, the pneumatic tire 1 employs the following configuration in order to improve the bead crack resistance.

  FIG. 2 is an enlarged view showing a bead portion of the pneumatic tire shown in FIG. 1. The figure shows a bead portion on one side before the rim is mounted (when the tire alone). Moreover, in the same figure, the intermediate rubber layer 18 and the buffer rubber layer 19 described later are hatched.

  As shown in FIG. 2, the pneumatic tire 1 includes an intermediate rubber layer 18 in a rim fitting portion (a portion fitted to the rim flange portion 101 at the time of inflation) of the bead portion. Therefore, the rim fitting portion of the bead portion has a two-color structure including the rim cushion rubber 17 and the intermediate rubber layer 18.

  The intermediate rubber layer 18 is made of a rubber material having a higher modulus than that of the rim cushion rubber 17. That is, the modulus M1 of the intermediate rubber layer 18 and the modulus M0 of the rim cushion rubber 17 have a relationship of M0 <M1.

  The modulus is a modulus at 100% elongation, and is measured by a tensile test at room temperature according to JIS K6251 (using No. 3 dumbbell).

  For example, in the configuration of FIG. 2, the modulus M1 of the intermediate rubber layer 18 and the modulus M0 of the rim cushion rubber 17 have a relationship of 1.10 ≦ M1 / M0 ≦ 1.80. Further, the modulus M1 of the intermediate rubber layer 18 is set within a range of 7.0 [MPa] ≦ M1 ≦ 8.0 [MPa], and the modulus M0 of the rim cushion rubber 17 is 4.5 [MPa] ≦ M0 ≦. It is set within the range of 6.4 [MPa]. Thereby, the relationship between the modulus M1 of the intermediate rubber layer 18 and the modulus M0 of the rim cushion rubber 17 is optimized.

  Further, the breaking elongation B1 and the rubber hardness H1 of the intermediate rubber layer 18 are set substantially the same as the breaking elongation B0 and the rubber hardness H0 of the rim cushion rubber 17. Specifically, the breaking elongation B1 and rubber hardness H1 of the intermediate rubber layer 18 and the breaking elongation B0 and rubber hardness H0 of the rim cushion rubber 17 are 0.80 ≦ B1 / B0 ≦ 1.80 and 0.90 ≦. It has a relationship of H1 / H0 ≦ 1.15. The breaking elongation B1 of the intermediate rubber layer 18 is set in a range of 250 [%] ≦ B1, and the breaking elongation B0 of the rim cushion rubber 17 is set in a range of 200 [%] ≦ B0 ≦ 310 [%]. Yes. Further, the rubber hardness H1 of the intermediate rubber layer 18 is set in the range of 65 ≦ H1 ≦ 75, and the rubber hardness H0 of the rim cushion rubber 17 is set in the range of 66 ≦ H0 ≦ 72. The upper limit of the breaking elongation B1 of the intermediate rubber layer 18 and the breaking elongation B0 of the rim cushion rubber 17 are not particularly limited, but are restricted by these other physical properties.

  The intermediate rubber layer 18 is disposed between the rim cushion rubber 17 and the carcass layer 13.

  For example, in the configuration of FIG. 2, as described above, the bead filler 12 is disposed outside the bead core 11 in the tire radial direction, and the carcass layer 13 is wound up outward in the tire radial direction so as to wrap the bead core 11 and the bead filler 12. Has been placed. In addition, the reinforcement 20 is disposed along the turn-up portion of the carcass layer 13 so as to wrap the turn-up portion of the carcass layer 13 and covers the turn-up end portion of the carcass layer 13 from the outside in the tire width direction. The intermediate rubber layer 18 is disposed outside the bead portion with respect to the carcass layer 13 and the reinforcement 20. A rim cushion rubber 17 is disposed so as to cover the entire intermediate rubber layer 18. Therefore, the intermediate rubber layer 18 is covered with the rim cushion rubber 17 and embedded in the bead portion so as not to be exposed on the surface of the bead portion.

  Further, the intermediate rubber layer 18 is disposed in a region where the amount of deformation of the rubber material during rolling of the tire is large in the rim fitting portion of the bead portion. Specifically, as shown in FIG. 2, the intermediate rubber layer 18 is at a position including at least a region from the bead heel P of the bead portion to the fitting end Q on the outer side in the tire radial direction of the fitting surface with respect to the rim flange portion 101. Be placed.

  The bead heel P refers to a point on the most heel side of the back of the foot when the bead portion is regarded as a human foot in a cross-sectional view in the tire meridian direction. As shown in FIG. 11, a rim flange portion 101 of a general rim 10 includes a flat portion 102 extending in the direction of the rotation axis of the rim 10 and a flat portion 102 in a sectional view of a plane including the rotation axis of the rim 10. And a convex portion 103 rising outward in the radial direction of the rim 10. In the inflated state of the pneumatic tire 1, the rim fitting portion of the bead portion is pressed against the flat portion 102 and the convex portion 103 of the rim flange portion 101 and comes into surface contact. At this time, the bead heel P is located at the boundary between the flat portion 102 of the rim flange portion 101 and the convex portion 103 (the rising point of the convex portion 103).

  In addition, the point (illustration omitted) which is the toe side most among said foot soles is called bead toe.

  The fitting end Q is a point on the outermost side in the tire radial direction among the bead portion, the rim flange portion 101, and the fitting surface in a sectional view in the tire meridian direction. For example, in the applicable rim defined by JATMA for the pneumatic tire 1 having a tire size of 12R22.5, the surface length L of the fitting surface from the bead heel P to the fitting end Q in a sectional view in the tire meridian direction is L = 12. 7 [mm].

  The bead heel P and the fitting end Q are defined as an unloaded state while attaching a tire to a specified rim and applying a specified internal pressure.

  Here, the prescribed rim refers to “applied rim” prescribed in JATMA, “Design Rim” prescribed in TRA, or “Measuring Rim” prescribed 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. However, in JATMA, in the case of tires for passenger cars, the specified internal pressure is air pressure 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

  For example, in the configuration of FIG. 2, the intermediate rubber layer 18 extends along the rim fitting portion of the bead portion so as to include a region (surface length L region) from the bead heel P to the fitting end Q. ing. Therefore, the end of the intermediate rubber layer 18 on the inner side in the tire width direction is on the inner side of the bead heel P in the tire width direction, and the end of the intermediate rubber layer 18 on the outer side in the tire radial direction is more than the fitting end Q. It is on the outer side in the tire radial direction.

  At this time, the distance Din in the surface length direction of the bead portion between the inner end in the tire width direction of the intermediate rubber layer 18 and the bead heel P is in the range of 0 [mm] ≦ Din, and 0.0 [mm ] ≦ Din ≦ 15.0 [mm] is preferable. Further, the distance Dout in the surface length direction of the bead portion between the end portion in the tire radial direction of the intermediate rubber layer 18 and the fitting end Q is in the range of 0 [mm] ≦ Dout, and 0.0 [ mm] ≦ Dout ≦ 20.0 [mm] is preferable.

  The distances Din and Dout are defined as a no-load state while applying a specified internal pressure by mounting the tire on a specified rim.

  In the configuration of FIG. 2, the maximum gauge t1 of the intermediate rubber layer 18 is set in a range of 1.5 [mm] ≦ t1. Further, the minimum gauge t0 of the rim cushion rubber 17 at the lap position with the intermediate rubber layer 18 is set in a range of 1.0 [mm] ≦ t0.

  The gauges t1 and t0 are measured as the thickness in the normal direction of the fitting surface of the bead portion with respect to the rim 10 when the tire is a single body and in an unloaded state. The upper limit of the maximum gauge t1 of the intermediate rubber layer 18 is not particularly limited, but is limited by the relationship with the minimum gauge t0 of the rim cushion rubber 17.

  As described above, in the pneumatic tire 1, the intermediate rubber layer 18 having a higher modulus than the rim cushion rubber 17 is disposed between the rim cushion rubber 17 and the carcass layer 13 (see FIG. 2). Accordingly, the intermediate rubber layer 18 is disposed in a region where the movement is large when the tire rolls. Then, when a compressive stress is repeatedly applied to the rim fitting portion of the bead portion during rolling of the tire (see FIG. 11), the intermediate rubber layer 18 functions as a buffer member and reduces the movement of the rim cushion rubber 17. Thereby, generation | occurrence | production of the crack in the rim cushion rubber | gum 17 is suppressed.

[Buffer rubber layer]
In addition, as shown in FIG. 2, the pneumatic tire 1 includes a buffer rubber layer 19. The buffer rubber layer 19 is a rubber member that absorbs strain energy around fibers and wires due to bending stress of the rim flange portion. Further, since the buffer rubber layer 19 has the above function, it is made of rubber having lower hardness and modulus and higher elongation at break than the intermediate rubber layer 18.

  For example, in the configuration of FIG. 2, the buffer rubber layer 19 has the following physical properties. First, the modulus M2 of the buffer rubber layer 19 is set in the range of 2.0 [MPa] ≦ M2 ≦ 4.0 [MPa]. Further, the breaking elongation B2 of the buffer rubber layer 19 is set in a range of 400 [%] ≦ B2. Further, the rubber hardness H2 of the buffer rubber layer 19 is set in a range of 52 ≦ H2 ≦ 64. The breaking elongation B2 of the buffer rubber layer 19 has no particular upper limit, but is restricted by other physical properties.

  The buffer rubber layer 19 is disposed between the rim cushion rubber 17 and the carcass layer 13 and on the outer side in the tire radial direction with respect to the intermediate rubber layer 18.

  For example, in the configuration of FIG. 2, the buffer rubber layer 19 is disposed between the side wall rubber 16 and the rim cushion rubber 17, the winding portion of the carcass layer 13, and the reinforcement 20. Specifically, the reinforcement 20 is disposed on the outer side in the tire width direction of the winding portion of the carcass layer 13, and the shock absorbing rubber layer 19 is disposed on the outer side in the tire width direction of the reinforcement 20 along the reinforcement 20. It extends in the tire radial direction. Further, the buffer rubber layer 19 and the intermediate rubber layer 18 are arranged side by side in the tire radial direction along the reinforcement 20 while wrapping each other in the tire radial direction. The sidewall rubber 16 and the rim cushion rubber 17 are disposed so as to cover the cushion rubber layer 19 from the outer side in the tire width direction while wrapping each other in the tire radial direction. Thereby, the buffer rubber layer 19 is embedded inside the bead portion without being exposed.

  In the above configuration, when the compressive stress is repeatedly applied to the rim fitting portion of the bead portion at the time of rolling of the tire (see FIG. 11), the buffer rubber layer 19 functions as a buffer member and moves the rim cushion rubber 17. Reduce. Thereby, generation | occurrence | production of the crack in the rim cushion rubber | gum 17 is suppressed.

[Modification]
3-9 is explanatory drawing which shows the modification of the pneumatic tire described in FIG. In these drawings, the same components as those of the pneumatic tire 1 described in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  In the configuration of FIG. 2, as described above, the intermediate rubber layer 18 and the buffer rubber layer 19 are arranged side by side in the tire radial direction along the reinforcement 20 while wrapping each other in the tire radial direction. Further, the buffer rubber layer 19 is disposed on the inner side in the tire width direction, and the intermediate rubber layer 18 is disposed so as to cover the end portion on the inner side in the tire radial direction of the intermediate rubber layer 18 from the outer side in the tire width direction.

  However, the present invention is not limited to this, and as shown in FIG. 3, the intermediate rubber layer 18 is disposed on the inner side in the tire width direction, and the cushioning rubber layer 19 extends from the outer side in the tire width direction to the end portion on the outer side in the tire radial direction. It may be placed over.

  2 and 3, as described above, the intermediate rubber layer 18 and the buffer rubber layer 19 are disposed so as to wrap in the tire radial direction (partially overlap each other). .

  However, the present invention is not limited to this, and as shown in FIG. 4, the intermediate rubber layer 18 and the buffer rubber layer 19 may be arranged with their ends in contact with each other in the tire radial direction without wrapping. Further, as shown in FIG. 5, the intermediate rubber layer 18 and the buffer rubber layer 19 may be disposed separately from each other. Even in these configurations, the movement of the rim cushion rubber 17 during rolling of the tire is reduced by the intermediate rubber layer 18 and the buffer rubber layer 19, and the occurrence of cracks in the rim cushion rubber 17 is suppressed.

  Further, in the configuration of FIG. 2, the reinforcement 20 is disposed so as to cover the winding portion of the carcass layer 13 from the outer side in the tire width direction. Further, the intermediate rubber layer 18 and the buffer rubber layer 19 are arranged on the outer side in the tire width direction of the reinforcement 20, and are arranged side by side in the tire radial direction along the reinforcement 20.

  However, the present invention is not limited thereto, and the reinforcement 20 may be omitted as shown in FIG. For example, in the configuration of FIG. 6, the intermediate rubber layer 18 is disposed in direct contact with the rolled-up portion of the carcass layer 13 from the tire width direction.

  Further, in the configuration of FIG. 2, the intermediate rubber layer 18 has a crescent shape in a cross-sectional view in the tire meridian direction, and is disposed with the ventral side facing the carcass layer 13 side. For this reason, the intermediate rubber layer 18 has a shape in which the width is increased from the rim cushion rubber 17 side (the rim fitting surface side of the bead portion) toward the carcass layer 13 side.

  On the other hand, in the configuration of FIGS. 7 to 9, the intermediate rubber layer 18 has a substantially rectangular shape (FIG. 7), a substantially trapezoidal shape (FIG. 8), and a substantially triangular shape (FIG. 9). Thus, the shape of the intermediate rubber layer 18 can be selected as appropriate.

[effect]
As described above, the pneumatic tire 1 includes a pair of bead cores 11, 11, a carcass layer 13 that spans the pair of bead cores 11, 11, and a rim that is disposed inside the carcass layer 13 in the tire radial direction. A pair of rim cushion rubbers 17 and 17 respectively constituting the fitting surface of the bead portion with respect to the flange portion 101 (see FIG. 11) are provided (see FIG. 1). The pneumatic tire 1 includes an intermediate rubber layer 18 disposed between the rim cushion rubber 17 and the carcass layer 13 (see FIG. 2). Further, the modulus M1 of the intermediate rubber layer 18 and the modulus M0 of the rim cushion rubber 17 have a relationship of M0 <M1.

  In such a configuration, the intermediate rubber layer 18 having a higher modulus than that of the rim cushion rubber 17 is disposed between the rim cushion rubber 17 and the carcass layer 13 (see FIG. 2). Then, when a compressive stress is repeatedly applied to the rim fitting portion of the bead portion during rolling of the tire (see FIG. 11), the intermediate rubber layer 18 functions as a buffer member and reduces the movement of the rim cushion rubber 17. Thereby, generation | occurrence | production of the crack in the rim cushion rubber | gum 17 is suppressed, and there exists an advantage which the bead crack-proof performance of a tire improves.

  In the pneumatic tire 1, the intermediate rubber layer 18 is disposed at a position including at least a region from the bead heel P of the bead portion to the fitting end Q on the outer side in the tire radial direction of the fitting surface with respect to the rim flange portion 101. (See FIG. 2). In such a configuration, since the intermediate rubber layer 18 is disposed in a region (region from the bead heel P to the fitting end Q) where the movement is large when the tire rolls, occurrence of cracks in the rim cushion rubber 17 is effectively suppressed. There are advantages.

  In the pneumatic tire 1, the modulus M1 of the intermediate rubber layer 18 is in the range of 7.0 [MPa] ≦ M1 ≦ 8.0 [MPa], and the modulus M0 of the rim cushion rubber 17 is 4.5. [MPa] ≦ M0 ≦ 6.4 [MPa]. Thereby, there is an advantage that the modulus M1 of the intermediate rubber layer 18 and the modulus M0 of the rim cushion rubber 17 are optimized.

  Further, in this pneumatic tire 1, the breaking elongation B1 and rubber hardness H1 of the intermediate rubber layer 18 and the breaking elongation B0 and rubber hardness H0 of the rim cushion rubber 17 are substantially the same. In such a configuration, since the difference in rigidity between the intermediate rubber layer 18 and the rim cushion rubber 17 is alleviated, there is an advantage that the occurrence of separation at the joint between the intermediate rubber layer 18 and the rim cushion rubber 17 is suppressed.

  Further, in the pneumatic tire 1, the breaking elongation B1 of the intermediate rubber layer 18 is in the range of 250 [%] ≦ B1, and the breaking elongation B0 of the rim cushion rubber 17 is 200 [%] ≦ B0 ≦ 310 [%]. Is in range. Accordingly, there is an advantage that the breaking elongation B1 of the intermediate rubber layer 18 and the breaking elongation B0 of the rim cushion rubber 17 are optimized.

  In the pneumatic tire 1, the rubber hardness H1 of the intermediate rubber layer 18 is in the range of 65 ≦ H1 ≦ 75, and the rubber hardness H0 of the rim cushion rubber 17 is in the range of 66 ≦ H0 ≦ 72. Thereby, there is an advantage that the rubber hardness H1 of the intermediate rubber layer 18 and the rubber hardness H0 of the rim cushion rubber 17 are optimized.

  Further, in this pneumatic tire 1, the distance Din in the surface length direction of the bead portion between the end portion in the tire width direction of the intermediate rubber layer 18 and the bead heel P is 0.0 [mm] ≦ Din ≦ 15.0. Within the range of [mm] (see FIG. 2). Thereby, there exists an advantage by which the position of the edge part inside the tire width direction of the intermediate | middle rubber layer 18 is optimized. That is, when 0.0 [mm] ≦ Din, the function of the intermediate rubber layer 18 as a buffer member is appropriately ensured. Further, by satisfying Din ≦ 15.0 [mm], the strength of the entire rim fitting portion of the bead portion is appropriately ensured.

  Further, in this pneumatic tire 1, the distance Dout in the surface length direction of the bead portion between the end portion in the tire radial direction of the intermediate rubber layer 18 and the fitting end Q is 0.0 [mm] ≦ Dout ≦ 20. Within the range of 0.0 [mm] (see FIG. 2). Thereby, there exists an advantage by which the position of the edge part of the tire radial direction outer side of the intermediate | middle rubber layer 18 is optimized. That is, when 0.0 [mm] ≦ Dout, the function of the intermediate rubber layer 18 as a buffer member is appropriately ensured. Further, by satisfying Dout ≦ 20.0 [mm], the strength of the entire rim fitting portion of the bead portion is appropriately ensured.

  In the pneumatic tire 1, the maximum gauge t1 of the intermediate rubber layer 18 is in the range of 1.5 [mm] ≦ t (see FIG. 2). Thereby, there exists an advantage by which the effect | action as a buffer member of the intermediate | middle rubber layer 18 is ensured appropriately.

  Further, in the pneumatic tire 1, the minimum gauge t0 of the rim cushion rubber 17 at the lap position with the intermediate rubber layer 18 is in a range of 1.0 [mm] ≦ t0 (see FIG. 2). Thereby, there exists an advantage by which the minimum gauge t0 of the rim cushion rubber | gum 17 is optimized. That is, when 1.0 [mm] ≦ t0, the strength of the rim cushion rubber 17 as the rim fitting portion is appropriately secured.

  Further, in the pneumatic tire 1, the intermediate rubber layer 18 has a shape in which the width is widened from the rim cushion rubber 17 side toward the carcass layer 13 side (inside the bead portion) in a sectional view in the tire meridian direction. (See FIGS. 2, 8 and 9) In such a configuration, since the intermediate rubber layer 18 has a wide structure on the carcass layer 13 side, the thickness of the intermediate rubber layer 18 is increased at a position where the distortion is greatest when contacting the rim flange portion. Thereby, there exists an advantage which can suppress generation | occurrence | production of a bead crack.

  In the pneumatic tire 1, the pneumatic tire 1 is disposed between the rim cushion rubber 17 and the carcass layer 13 and on the outer side in the tire radial direction with respect to the intermediate rubber layer 18, and has lower hardness and lower than the intermediate rubber layer 18. A shock-absorbing rubber layer 19 made of a rubber material having a modulus and a high elongation at break is provided (see FIG. 2). With such a configuration, the shock absorbing rubber layer 19 is disposed on the outer side in the tire radial direction of the intermediate rubber layer 18, so that the buffer structure of the bead portion is appropriately secured and the bead crack resistance performance of the tire is improved.

  Moreover, in this pneumatic tire 1, the intermediate | middle rubber layer 18 and the buffer rubber layer 19 are mutually wrapped and arrange | positioned (refer FIG. 2 and FIG. 3). This has the advantage that the occurrence of air failures is less than when molding without lapping.

  The pneumatic tire 1 includes a reinforcement 20 disposed between the carcass layer 13 and the intermediate rubber layer 18 (see FIG. 2). In such a configuration, since the reinforcement 20 is interposed between the intermediate rubber layer 18 (and the buffer rubber layer 19) and the winding end of the carcass layer 13, the intermediate rubber layer 18 starting from the winding end of the carcass layer 13 is used. There is an advantage that the occurrence of separation of (or the buffer rubber layer 19) is suppressed.

  FIG. 10 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  In this performance test, evaluation regarding bead crack resistance was performed for a plurality of different pneumatic tires (see FIG. 10). This performance test is performed by a low-pressure endurance test using an indoor drum tester. Further, a pneumatic tire having a tire size of 12R22.5 is assembled to an applicable rim defined by JATMA, and an air pressure of 1200 [kPa] and a load of 51.52 [kN] are applied to the pneumatic tire. Then, the vehicle is run for 20 days with the running speed set to 45 [km / h], and thereafter, cracks and separation generated in the bead portion are observed and evaluated. This evaluation is performed by index evaluation based on a conventional example, and the larger the value, the smaller the breakage of the bead portion, which is preferable.

  The pneumatic tires 1 of Examples 1 to 7 have the configurations described in FIGS. 1 and 2, and include an intermediate rubber layer 18 and a buffer rubber layer 19 in the rim fitting portion of the bead portion. The modulus M0 of the rim cushion rubber 17 is M0 = 5.5 [kPa], the breaking elongation B0 is B0 = 250 [%], and the hardness H0 is H0 = 69. The modulus M2 of the buffer rubber layer 19 is M2 = 3.0 [kPa], the breaking elongation B2 is B2 = 410 [%], and the hardness H2 is H2 = 61.

  The conventional pneumatic tire does not include the intermediate rubber layer 18 in the pneumatic tire 1 of the first embodiment.

  As shown in the test results, it can be seen that in the pneumatic tires 1 of Examples 1 to 7, the bead crack resistance performance of the tire is improved.

  1: Pneumatic tire, 11: Bead core, 12: Bead filler, 121: Lower filler, 122: Upper filler, 13: Carcass layer, 14: Belt layer, 141-144: Belt ply, 15: Tread rubber, 16: Side Wall rubber, 17: Rim cushion rubber, 18: Intermediate rubber layer, 19: Buffer rubber layer, 20: Reinforce, 101: Rim flange part, 10: Rim, 102: Flat part, 103: Convex part

Claims (13)

A pair of bead cores, a carcass layer spanned between the pair of bead cores, a pair of rim cushion rubbers disposed on the inner side in the tire radial direction of the carcass layer and constituting a fitting surface of the bead portion with respect to the rim flange portion, respectively A pneumatic tire comprising:
An intermediate rubber layer disposed between the rim cushion rubber and the carcass layer, and a buffer disposed between the rim cushion rubber and the carcass layer and on the outer side in the tire radial direction with respect to the intermediate rubber layer. for example Bei and the rubber layer,
Wherein the modulus M1 of the intermediate rubber layer, and the modulus M0 of the rim cushion rubber, have a relationship M0 <M1,
The modulus M2 of the buffer rubber layer is 2.0 [MPa] ≦ M2 ≦ 4.0 [MPa],
The breaking elongation B2 of the buffer rubber layer is 400 [%] ≦ B2, and
A pneumatic tire characterized in that a rubber hardness H2 of the buffer rubber layer is 52 ≦ H2 ≦ 64 .   2. The pneumatic tire according to claim 1, wherein the intermediate rubber layer is disposed at a position including at least a region from a bead heel P of the bead portion to a fitting end Q on the outer side in the tire radial direction of the fitting surface with respect to the rim flange portion.   The modulus M1 of the intermediate rubber layer is in the range of 7.0 [MPa] ≦ M1 ≦ 8.0 [MPa], and the modulus M0 of the rim cushion rubber is 4.5 [MPa] ≦ M0 ≦ 6.4. The pneumatic tire according to claim 1 or 2, which is in a range of [MPa]. The breaking elongation B1 and rubber hardness H1 of the intermediate rubber layer and the breaking elongation B0 and rubber hardness H0 of the rim cushion rubber are 0.80 ≦ B1 / B0 ≦ 1.80 and 0.90 ≦ H1 / H0 ≦ 1. . The pneumatic tire according to claim 1 , having a relationship of .15 .   The breaking elongation B1 of the intermediate rubber layer is in a range of 250 [%] ≦ B1, and the breaking elongation B0 of the rim cushion rubber is in a range of 200 [%] ≦ B0 ≦ 310 [%]. Pneumatic tires.   The pneumatic tire according to claim 4 or 5, wherein a rubber hardness H1 of the intermediate rubber layer is in a range of 65≤H1≤75, and a rubber hardness H0 of the rim cushion rubber is in a range of 66≤H0≤72. .   The distance Din in the surface length direction of the bead portion between the inner end in the tire width direction of the intermediate rubber layer and the bead heel P is in the range of 0.0 [mm] ≦ Din ≦ 15.0 [mm]. The pneumatic tire according to any one of Items 1 to 6.   The distance Dout in the surface length direction of the bead portion between the end portion in the tire radial direction of the intermediate rubber layer and the fitting end Q is in the range of 0.0 [mm] ≦ Dout ≦ 20.0 [mm]. The pneumatic tire according to any one of claims 1 to 7.   The pneumatic tire according to any one of claims 1 to 8, wherein a maximum gauge t1 of the intermediate rubber layer is in a range of 1.5 [mm] ≤ t1.   The pneumatic tire according to any one of claims 1 to 9, wherein a minimum gauge t0 of the rim cushion rubber at a lap position with the intermediate rubber layer is in a range of 1.0 [mm] ≤ t0.   The pneumatic according to any one of claims 1 to 10, wherein the intermediate rubber layer has a shape in which a width is widened from the rim cushion rubber side toward the carcass layer side in a sectional view in a tire meridian direction. tire. The pneumatic tire according to any one of claims 1 to 11 , wherein the intermediate rubber layer and the buffer rubber layer are disposed so as to be wrapped with each other. The pneumatic tire according to any one of claims 1 to 12 , further comprising a reinforcement disposed between the carcass layer and the intermediate rubber layer.

Images