JP2019171976A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire capable of improving a ride comfort performance and rim assembly performance while restraining degradation of steering stability performance.SOLUTION: A pneumatic tire includes a carcass having carcass plies 6A, 6B, and a reinforcing rubber 9 disposed outside the carcass in a tire axial direction in a bead part 4. The reinforcing rubber 9 includes a first reinforcing rubber 11 forming an exterior surface 4A of the bead part 4, and a second reinforcing rubber 12 smaller in complex elastic modulus than the first reinforcing rubber 11. The inner end 12i of the second reinforcing rubber 12 in a tire radial direction is located inside the outer end 5e of a bead core 5 in the tire radial direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire having a reinforcing rubber in a bead portion.

  The following Patent Document 1 describes a tire provided with a core, a carcass, and a filler. The core is disposed on the radially inner side of the tire. The carcass has a folded portion disposed on the outer side in the axial direction of the core. The filler is disposed on the outer side in the axial direction of the folded portion. Patent Document 1 describes that when the complex elastic modulus of the filler is reduced, a decrease in riding comfort is suppressed.

  However, simply reducing the complex elastic modulus of the filler reduces the rigidity in the vicinity of the core, so that there is a problem that the tightening force of the core is reduced and the steering stability performance is deteriorated.

JP-A-2006-130053

  The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire that can improve ride comfort performance and rim assembly performance while suppressing deterioration in steering stability performance. Yes.

  The present invention relates to a carcass having a carcass ply including a main body part extending from a tread part through a sidewall part to a bead core of a bead part, and a folded part folded around the bead core, and the carcass ply at the bead part. A pneumatic tire including a reinforcing rubber disposed on an outer side of the folded portion in a tire axial direction, wherein the reinforcing rubber includes a first reinforcing rubber that forms an outer surface of the bead portion, and the first reinforcing rubber. A second reinforcing rubber having a smaller complex elastic modulus, and an inner end in the tire radial direction of the second reinforcing rubber is located on an inner side in the tire radial direction than an outer end in the tire radial direction of the bead core.

  In the pneumatic tire according to the present invention, it is desirable that the inner end of the second reinforcing rubber is located on the inner side in the tire radial direction than the innermost position in the tire radial direction of the carcass.

  In the pneumatic tire according to the present invention, it is preferable that the inner end of the second reinforcing rubber is located inside the tire axial direction of the bead core in the tire axial direction.

  In the pneumatic tire according to the present invention, it is desirable that the second reinforcing rubber is disposed on the inner side in the tire axial direction of the first reinforcing rubber.

  In the pneumatic tire according to the present invention, a part of the first reinforcing rubber is disposed on the inner side in the tire radial direction with respect to the outer end of the bead core, and on the inner side in the tire radial direction with respect to the outer end of the bead core. The cross-sectional area of the second reinforcing rubber is preferably 10% to 50% of the cross-sectional area of the first reinforcing rubber.

  In the pneumatic tire according to the present invention, it is desirable that an outer end of the second reinforcing rubber in the tire radial direction is located on an outer side in the tire radial direction of the outer end of the first reinforcing rubber in the tire radial direction.

  The pneumatic tire of the present invention has a first reinforcing rubber that forms an outer surface of a bead portion, a complex elastic modulus that is smaller than that of the first reinforcing rubber, and an inner side in the tire axial direction of the first reinforcing rubber. And a second reinforcing rubber. The inner end of the second reinforcing rubber in the tire radial direction is located on the inner side in the tire radial direction than the outer end of the bead core in the tire radial direction. Thereby, since the vibration transmitted from the road surface to the bead core is absorbed by the second reinforcing rubber, the riding comfort performance is improved. The second reinforcing rubber reduces the rigidity of the bead core on the outer side in the tire axial direction. For this reason, when assembling the rim, the contact pressure between the bead portion and the hump for preventing rim removal provided on the rim seat surface of the rim is reduced. Thereby, since a bead part can get over a hump smoothly, rim assembly performance improves.

  In the pneumatic tire of the present invention, the first reinforcing rubber suppresses a large decrease in the rigidity of the bead portion, and restrains movement (deformation) of the bead core in the tire radial direction or movement in the tire axial direction. Maintain high bead core tightening force. For this reason, reduction of steering stability performance is suppressed.

  Therefore, the pneumatic tire of the present invention provides excellent ride comfort performance and rim assembly performance while suppressing reduction in steering stability performance.

It is a tire meridian sectional view showing one embodiment of a pneumatic tire of the present invention. It is an enlarged view of the bead part of FIG. It is a figure which shows notionally cross-sectional areas, such as reinforcement rubber | gum.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis (not shown) in a normal state of a pneumatic tire (hereinafter simply referred to as “tire”) 1 showing an embodiment of the present invention. In the present embodiment, as a preferable aspect, for example, a tire 1 for a four-wheel drive vehicle such as an SUV that can travel on a gravel road as well as a paved road is shown. However, the present invention is not limited to such an embodiment.

  The “normal state” is a state in which the tire 1 is assembled on a normal rim (not shown), is filled with a normal internal pressure, and is unloaded. Hereinafter, unless otherwise specified, dimensions and the like of each part of the tire 1 are values measured in this normal state.

  The “regular rim” is a rim determined by each tire in the standard system including the standard on which the tire 1 is based. For example, “standard rim” for JATMA, “Design Rim” for TRA, For ETRTO, it is "Measuring Rim".

  “Normal internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire 1 is based. “JTMA” is the “highest air pressure”, TRA is the table “TIRE LOAD” Maximum value described in “LIMITSAT VARIOUSCOLD INFLATION PRESSURES”, “INFLATION PRESSURE” in ETRTO.

  As shown in FIG. 1, the tire 1 of the present embodiment includes a carcass 6, a tread reinforcing layer 7, and a reinforcing rubber 9.

  The carcass 6 is formed of two carcass plies 6A and 6B at least one, in the present embodiment, inside and outside in the tire radial direction. Each of the carcass plies 6 </ b> A and 6 </ b> B has a carcass cord arranged with an inclination of, for example, 75 to 90 ° with respect to the tire equator C. As the carcass cord, for example, an organic fiber cord such as nylon, polyester, or rayon is suitably employed.

  Each carcass ply 6A, 6B includes main body portions 6a, 6c and folded portions 6b, 6d, respectively. Each of the main body portions 6 a and 6 c reaches the bead core 5 of the bead portion 4 from the tread portion 2 through the sidewall portion 3. The folded portions 6b and 6d are connected to the main body portions 6a and 6c, respectively, are turned around the bead core 5 from the inner side in the tire axial direction to the outer side, rise to the outer side in the tire radial direction, and terminate.

  The inner carcass ply 6 </ b> A has an innermost position 6 i of the carcass 6 on the inner side of the bead core 5 in the tire radial direction.

  Between the main body portion 6c and the folded portion 6d of the outer carcass ply 6B, a bead apex rubber 8 having a substantially triangular cross section extending from the bead core 5 to the outer side in the tire radial direction is provided.

  The tread reinforcing layer 7 is disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2. The tread reinforcing layer 7 is composed of at least one belt ply 7A and 7B inside and outside in the tire radial direction in this embodiment. The belt plies 7A and 7B are formed, for example, by covering an array of belt cords with a topping rubber. The belt cords of the belt plies 7A and 7B are preferably highly elastic such as steel cords.

  In the present embodiment, the tire 1 is provided with an inner liner 10 made of air-impermeable rubber, which forms the inner surface of the carcass 6 in the tire axial direction and forms the lumen surface 1a of the tire 1. In this embodiment, the inner liner 10 is provided across the bead cores 5.

  The bead core 5 is formed in, for example, a polygonal cross-section in which steel bead wires (not shown) are wound in multiple rows and stages.

  FIG. 2 is an enlarged view of the bead portion 4. As shown in FIG. 2, the bead core 5 of the present embodiment is formed in, for example, a quadrangular cross section, and has an upper surface 5a extending in the tire axial direction on the outer side in the tire radial direction and a lower surface extending in the tire axial direction on the inner side in the tire radial direction. 5b. The upper surface 5a of the present embodiment has an outer end 5e of the bead core 5 in the tire radial direction. The lower surface 5b of the present embodiment has an inner end 5i of the bead core 5 in the tire radial direction.

  The reinforcing rubber 9 of the present embodiment is disposed on the outer side in the tire axial direction of the folded portion 6b of the inner carcass ply 6A in the bead portion 4.

  In this embodiment, the reinforcing rubber 9 includes a first reinforcing rubber 11 that forms the outer surface 4 </ b> A of the bead portion 4, and a second reinforcing rubber 12 that has a complex elastic modulus smaller than that of the first reinforcing rubber 11. The inner end 12i of the second reinforcing rubber 12 in the tire radial direction is located on the inner side in the tire radial direction of the outer end 5e of the bead core 5 in the tire radial direction. As a result, the vibration transmitted from the road surface to the bead core 5 is absorbed by the second reinforcing rubber 12, so that the riding comfort performance is improved. Further, the second reinforcing rubber 12 reduces the rigidity of the bead core 5 on the outer side in the tire axial direction. For this reason, when assembling the rim, the contact pressure between the bead portion 4 and, for example, a rim detachment preventing hump (not shown) provided on the rim seat surface of the rim is reduced. Thereby, since the bead part 4 can get over a hump smoothly, rim assembly performance improves.

  The first reinforcing rubber 11 suppresses a large decrease in rigidity of the bead portion 4 and restrains the movement (deformation) of the bead core 5 in the tire radial direction or the movement in the tire axial direction. Keep it high. For this reason, reduction of steering stability performance is suppressed. Therefore, the tire 1 of the present embodiment has excellent ride comfort performance and rim assembly performance while suppressing reduction in steering stability performance.

For example, the second reinforcing rubber 12 is disposed on the inner side of the first reinforcing rubber 11 in the tire axial direction. Thereby, the vibration transmitted from the road surface to the bead core 5 is effectively absorbed by the second reinforcing rubber 12.

  In this embodiment, the inner end 12i of the second reinforcing rubber 12 is located on the inner side in the tire radial direction than the innermost position 6i of the carcass 6. Such a second reinforcing rubber 12 appropriately reduces the rigidity on the inner side in the tire radial direction than the bead core 5 and reduces the fitting pressure to the rim (not shown), so that the rim assembly workability is further improved. Further, such second reinforcing rubber 12 can more effectively absorb the vibration transmitted from the road surface to the bead core 5.

  In order to exhibit the above-described action more effectively, it is desirable that the inner end 12i of the second reinforcing rubber 12 is located inside the tire axial direction of the bead core 5 in the tire axial direction. In this embodiment, the inner end 12i of the second reinforcing rubber 12 terminates inside the tire axial direction from the inner end 5f of the bead core 5 in the tire axial direction and does not reach the lumen surface 1a of the tire 1. Yes. In this specification, the center 5c of the bead core 5 is the centroid of the bead core 5 in the tire meridian cross section. The second reinforcing rubber 12 may be configured to extend outward in the tire radial direction along the main body portion 6a so as to wind the bead core 5 from the outer side in the tire axial direction to the inner side (not shown).

  In the present embodiment, the second reinforcing rubber 12 is formed in an L-shaped cross section including the second outer portion 12A and the second inner portion 12B. The second outer portion 12A of the present embodiment extends in the tire radial direction along the folded portion 6b outside the bead core 5 in the tire axial direction. The second inner portion 12B of the present embodiment is disposed on the inner side of the bead core 5 in the tire radial direction and extends in the tire axial direction. Such second reinforcing rubber 12 can effectively absorb the vibration transmitted to the bead core 5 without transmitting it to the rim.

  In the present embodiment, the first reinforcing rubber 11 is formed in a J-shaped cross section including the first outer portion 11A, the first center portion 11B, and the first inner portion 11C. The first outer portion 11A of the present embodiment is disposed on the outer side in the tire axial direction of the second outer portion 12A and extends in the tire radial direction. For example, the first outer portion 11A is in contact with a rim flange surface (not shown) of the rim. The first central portion 11B of the present embodiment is arranged on the inner side in the tire radial direction than the second inner portion 12B and extends in the tire axial direction. The first central portion 11B is in contact with, for example, a rim base surface (not shown) of the rim. The first inner portion 11 </ b> C of the present embodiment is connected to the first central portion 11 </ b> B and extends in the tire radial direction along the lumen surface 1 a of the tire 1. The first reinforcing rubber 11 is not limited to such an aspect.

  The outer end 11e of the first reinforcing rubber 11 in the tire radial direction is desirably located on the inner side in the tire radial direction of the outer end 12e of the second reinforcing rubber 12 in the tire radial direction. As a result, the first reinforcing rubber 11 is prevented from coming into direct contact with the carcass 6, so that vibration from the road surface is absorbed by the second reinforcing rubber 12 without being transmitted to the first reinforcing rubber 11.

  In order to effectively exhibit the above-described action, the distance La in the tire radial direction between the outer end 11e of the first reinforcing rubber 11 and the outer end 12e of the second reinforcing rubber 12 is the tire cross-sectional height (FIG. 1). It is desirable that it is 2% or more of H. When the distance La is excessively large, the mass of the tire 1 may increase and the steering stability performance may be deteriorated. For this reason, the distance La is desirably 6% or less of the tire cross-section height H.

  FIG. 3 is a tire meridian cross-sectional view conceptually showing the cross-sectional areas of the first reinforcing rubber 11 and the second reinforcing rubber 12. As shown in FIG. 3, the cross-sectional area A2 of the second reinforcing rubber 12 is 10% to 50% of the cross-sectional area A1 of the first reinforcing rubber 11 inside the outer end 5e of the bead core 5 in the tire radial direction. It is desirable. When the cross-sectional area A2 is less than 10% of the cross-sectional area A1, the rigidity of the bead portion 4 on the inner side in the tire radial direction from the bead core 5 cannot be effectively reduced, and rim assembly workability and ride comfort performance are reduced. There is a risk that it cannot be increased. When the cross-sectional area A2 exceeds 50% of the cross-sectional area A1, the rigidity of the bead portion 4 on the inner side in the tire radial direction than the bead core 5 becomes excessively small, and the steering stability performance may be deteriorated. Therefore, the cross-sectional area A2 is more preferably 20% or more and more preferably 40% or less of the cross-sectional area A1.

  The cross-sectional area A4 of the second reinforcing rubber 12 is preferably 30% to 70% of the cross-sectional area A3 of the first reinforcing rubber 11 outside the outer end 5e of the bead core 5 in the tire radial direction. When the cross-sectional area A4 is less than 40% of the cross-sectional area A3, the vibration absorption effect may be reduced. When the cross-sectional area A4 exceeds 70% of the cross-sectional area A3, the rigidity of the bead portion 4 may be excessively reduced.

  The complex elastic modulus E * 1 of the first reinforcing rubber 11 is preferably 5 MPa or more. When the complex elastic modulus E * 1 of the first reinforcing rubber 11 is less than 5 MPa, the rigidity of the bead portion 4 cannot be effectively increased, and the steering stability performance may be deteriorated. When the complex elastic modulus E * 1 of the first reinforcing rubber 11 is excessively large, the longitudinal spring of the bead portion 4 becomes large, and the ride comfort performance may be deteriorated. For this reason, the complex elastic modulus E * 1 of the first reinforcing rubber 11 is desirably 25 MPa or less.

In this specification, “complex elastic modulus E *” is a value measured using a “viscoelastic spectrometer” manufactured by Iwamoto Seisakusho Co., Ltd. under the following conditions in accordance with the provisions of JIS-K6394. is there.
Initial strain: 10%
Amplitude: ± 1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70 ° C

  The complex elastic modulus E * 2 of the second reinforcing rubber 12 is desirably 20 MPa or less. When the complex elastic modulus E * 2 of the second reinforcing rubber 12 exceeds 20 MPa, the road surface vibration may not be effectively absorbed. When the complex elastic modulus E * 2 of the second reinforcing rubber 12 is excessively small, the fitting pressure with respect to the rim becomes too small, and there is a possibility that rim displacement is likely to occur. For this reason, the complex elastic modulus E * 2 of the second reinforcing rubber 12 is desirably 3 MPa or more.

  From such a viewpoint, it is desirable that the complex elastic modulus E * 2 of the second reinforcing rubber 12 is 5 to 25 MPa smaller than the complex elastic modulus E * 1 of the first reinforcing rubber 11.

  In order to exhibit the above-described action more effectively, the rubber hardness of the first reinforcing rubber 11 is preferably 65 to 95 degrees. The rubber hardness of the second reinforcing rubber 12 is desirably 55 to 90 degrees. Furthermore, the rubber hardness of the second reinforcing rubber 12 is desirably 5 to 15 degrees smaller than the rubber hardness of the first reinforcing rubber 11.

  In this specification, “rubber hardness” is hardness according to durometer type A in an environment of 23 ° C. in accordance with JIS-K6253.

  The complex elastic modulus E * 3 of the bead apex rubber 8 is desirably 5 to 25 MPa larger than the complex elastic modulus E * 2 of the second reinforcing rubber 12. Such a bead apex rubber 8 increases the lateral rigidity of the bead portion 4 and improves the steering stability performance. From the same viewpoint, the rubber hardness of the bead apex rubber 8 is desirably the same as the rubber hardness of the second reinforcing rubber 12 or a difference between the rubber hardness of the second reinforcing rubber 12 and 15 degrees or less.

  As shown in FIG. 2, the height Hb of the bead apex rubber 8 in the tire radial direction is 0.2 to 0. 0 of the height Ha in the tire radial direction from the outer end 5e of the bead core 5 of the second reinforcing rubber 12. 5 times is desirable. When the height Hb of the bead apex rubber 8 is less than 0.2 times the height Ha of the second reinforcing rubber 12, the rigidity of the bead portion 4 is reduced, and the steering stability performance may be deteriorated. When the height Hb of the bead apex rubber 8 exceeds 0.5 times the height Ha of the second reinforcing rubber 12, the rigidity of the bead portion 4 is excessively increased, and the ride comfort performance may be deteriorated.

  As shown in FIG. 3, the cross-sectional area A5 of the bead apex rubber 8 is the second reinforcing rubber 12 on the outer side in the tire radial direction from the outer end 5e of the bead core 5 in order to effectively exhibit the above-described action. The cross-sectional area A4 is preferably 40% to 80%.

  As mentioned above, although embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention is not limited to exemplary embodiment, and can be deform | transformed and implemented in a various aspect.

A pneumatic tire having a size of 275 / 65R18 having the basic structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1 and tested for ride comfort performance, steering stability performance, and rim assembly workability. The common specifications and test methods for each tire are as follows.
First reinforcing rubber: 15 MPa (complex elastic modulus), 72 degrees (rubber hardness)
Second reinforcing rubber: 8MPa (complex elastic modulus), 65 degrees (rubber hardness)
Bead apex rubber rubber: 9MPa (complex elastic modulus), 68 degrees (rubber hardness)
In Table 1, A: 3 mm away from the bead core in the radial direction of the tire. B: On the outer side in the tire axial direction of the bead core, between the outer end and the inner end in the tire radial direction. C: In the tire axial direction of the bead core. Outside, inner side in the tire radial direction than the innermost position in the tire radial direction of the carcass Same D: Inward in the tire radial direction from the innermost position in the carcass, and between the center of the bead core and the inner end 5f in the tire axial direction Position E: As described in FIG. 2 In Examples 1 to 5, the cross-sectional area A1 is the same.
In Examples 6 to 9, the cross-sectional area A3 + the cross-sectional area A4 is the same.
Examples 10 and 11 have the same cross-sectional area A4.

<Ride comfort and steering stability>
Sample tires were installed on all wheels of a 3700cc four-wheel drive vehicle under the following conditions. The test driver runs this vehicle on a dry asphalt road test course, and the test driver's sensation is the ride comfort performance related to stability during lane changes and straight running, and the steering stability performance related to driving, braking and turning. It was evaluated by. A result is a score which sets the comparative example 1 to 100, and it is so favorable that a numerical value is large.
Rim: 18 × 8.0J
Internal pressure: 230kPa

<Rim assembly workability>
The ease of fitting when each sample tire was mounted on a regular rim was evaluated by the operator's sensuality. A result is a score which sets the comparative example 1 to 100, and shows that it is easy to fit, so that a numerical value is large.
Table 1 shows the test results.

  As a result of the test, it was confirmed that the tires of the examples were suppressed in the deterioration of the steering stability performance and improved in the riding comfort performance as compared with the tires of the comparative examples. Further, it was confirmed that the rim assembly workability of the tire of the example was improved as compared with the tire of the comparative example. Further, the complex elastic modulus of the reinforcing rubber was changed within a preferable range, and the same result was obtained.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 4 Bead part 4A Outer surface 5 Bead core 5e Outer end 6 Carcass 9 Reinforcement rubber 11 1st reinforcement rubber 12 2nd reinforcement rubber 12i Inner end

Claims (6)

A carcass having a carcass ply including a main body part extending from the tread part through the sidewall part to the bead core of the bead part, and a folded part folded around the bead core, and the folded part of the carcass ply at the bead part A pneumatic tire including a reinforcing rubber disposed on the outer side in the tire axial direction,
The reinforcing rubber includes a first reinforcing rubber that forms an outer surface of the bead portion, and a second reinforcing rubber having a complex elastic modulus smaller than that of the first reinforcing rubber,
An inner end in the tire radial direction of the second reinforcing rubber is located on an inner side in the tire radial direction from an outer end in the tire radial direction of the bead core.
Pneumatic tire.   2. The pneumatic tire according to claim 1, wherein the inner end of the second reinforcing rubber is located on an inner side in the tire radial direction than an innermost position in the tire radial direction of the carcass.   The pneumatic tire according to claim 2, wherein the inner end of the second reinforcing rubber is located on the inner side in the tire axial direction than the center in the tire axial direction of the bead core.   The pneumatic tire according to any one of claims 1 to 3, wherein the second reinforcing rubber is disposed on an inner side of the first reinforcing rubber in the tire axial direction.   A part of the first reinforcing rubber is disposed on the inner side in the tire radial direction from the outer end of the bead core, and the cross-sectional area of the second reinforcing rubber is on the inner side in the tire radial direction from the outer end of the bead core. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is 10% to 50% of a cross-sectional area of the first reinforcing rubber.   The pneumatic end according to any one of claims 1 to 5, wherein an outer end of the second reinforcing rubber in a tire radial direction is located on an outer side in an tire radial direction of an outer end of the first reinforcing rubber in a tire radial direction. tire.

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