JP2005297752A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improving run flat durability without causing deterioration of ride comfort and road noise of a side reinforcing type run flat tire. <P>SOLUTION: In the run flat pneumatic tire, bead fillers 5 are respectively provided at a pair of right and left bead portions 3, and a reinforcing rubber layer 6 with a crescent-shaped cross section partially overlapping with the beat filler 5 is disposed on a side wall portion 2. Without disposing a reinforcing fiber layer except for a carcass layer 7 around the bead filler 5, the rubber physical property of at least outer peripheral side tip end portion of the bead filler 5 and the reinforcing rubber layer 6 is made to be 0.15 in tanδ and 5 to 15 MPa in dynamic modulus E1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that improves run-flat durability without deteriorating ride comfort and road noise of a side-reinforced run-flat tire.

  In so-called side-reinforced run-flat tires with a reinforced rubber layer inserted in the side wall, a high modulus rubber material is used for the reinforced rubber layer in order to reduce deformation of the side wall during run flat running. ing. However, since the high modulus rubber is embedded in the sidewall portion in this way, the sidewall portion near the upper end of the beadler often becomes an initial point of destruction during the run flat running.

Conventionally, there has been a proposal to insert a reinforcing fiber layer in the vicinity of the beadler as a measure for extending the breakage time of the sidewall portion as much as possible and extending the run-flat travel distance (Patent Document 1, etc.). However, by inserting the reinforcing fiber layer in this way, the longitudinal rigidity of the sidewall portion is increased, so that there is a problem that ride comfort and road noise are deteriorated.
Japanese Patent Laid-Open No. 5-112110

  An object of the present invention is to provide a pneumatic tire in which run-flat durability is improved without deteriorating ride comfort and road noise of a side-reinforced run-flat tire.

  In the pneumatic tire of the present invention that achieves the above object, a bead filler is disposed in each of the pair of left and right bead portions, and a reinforcing rubber layer having a crescent cross section that partially overlaps the bead filler is disposed in a sidewall portion. In the run-flat pneumatic tire, the tan δ of the rubber characteristics of at least the outer peripheral side tip portion of the bead filler and the reinforcing rubber layer is set to 0, without disposing a reinforcing fiber layer other than the carcass layer around the bead filler. 15 or less and the dynamic elastic modulus E1 is 5 to 15 MPa.

  According to the pneumatic tire of the present invention, the low-tan δ rubber is used at least on the outer peripheral side tip for the bead filler as well as the reinforcing rubber layer, so that heat generation near the upper end of the bead filler during run flat running can be suppressed. Thus, it is possible to extend the time until the side wall portion is damaged and to extend the distance that can be run flat. Moreover, the dynamic elastic modulus of the reinforcing rubber layer and the bead filler is set to 5 to 15 MPa without disposing the reinforcing fiber layer other than the carcass layer, so that it is possible to suppress the deterioration of ride comfort and road noise. it can. Furthermore, rolling resistance can be improved by using low tan δ rubber for the bead filler and the reinforcing rubber layer.

  The present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a meridian cross section showing a pneumatic tire according to an embodiment of the present invention.

  Reference numeral 1 denotes a tread portion. Side wall portions 2 and 2 and bead portions 3 and 3 extend radially inward on the left and right sides, respectively. A bead core 4 in which steel wires are bundled is embedded in each bead portion 3, and a bead filler 5 is provided on the outer peripheral side of the bead core 4 so as to extend radially outward. A reinforcing rubber layer 6 having a crescent cross section is inserted as a liner inside the sidewall portion 2. The reinforcing rubber layer 6 overlaps the radially inner end side with the outer peripheral end portion of the bead filler 5 and extends the radially outer end side to the tread portion 1 side.

  A plurality of belt layers 8 are provided on the outer peripheral side of the carcass layer 7 provided inside the tire. The carcass layer 7 passes from the outer peripheral portion of the tread portion 1 to the outside of the reinforcing rubber layers 6 and 6 of the left and right sidewall portions 2 and 2, passes through the inside of the bead fillers 5 and 5, and the bead cores 4 and 4 to the inside of the tire It is designed to fold back from the outside. Further, the end portions of the carcass layer 7 where the bead cores 4 and 4 are folded are overlapped on the carcass layer 7 covering the outside of the reinforcing rubber layers 6 and 6 via the outside of the bead fillers 5 and 5, respectively.

  FIG. 2 shows a pneumatic tire according to another embodiment of the present invention.

  In this embodiment, the bead filler 5 has a two-layer structure of an inner peripheral base portion 5a and an outer peripheral tip portion 5b, and other configurations are substantially the same as those of the embodiment of FIG.

  The pneumatic tire of the present invention is characterized in that no reinforcing fiber layer is disposed around the bead filler other than the carcass layer as described above. If the reinforcing fiber layer is disposed around the bead filler, the longitudinal rigidity of the sidewall portion is increased, which causes a deterioration in ride comfort and road noise.

  In the tire structure without the reinforcing fiber layer as described above, as a rubber material for at least the outer peripheral side tip of the bead filler and the reinforcing rubber layer, tan δ is 0.15 or less, preferably 0.10, and dynamic elasticity A rubber material having a rate E1 of 5 to 15 MPa, preferably 7 to 10 MPa is used. Although tan δ is preferably as low as possible, the lowest value that can be produced at present is about 0.01.

  With respect to the bead filler, it is only necessary that at least the outer peripheral tip that overlaps the reinforcing rubber layer in the radial direction satisfies the rubber physical properties of tan δ and the dynamic elastic modulus E1. That is, when the bead filler has a single-layer structure as in the embodiment of FIG. 1, the entire rubber physical properties are satisfied. However, as in the embodiment of FIG. 2, the bead filler has a two-layer structure. If there is, only the outer peripheral end portion 5b may satisfy the rubber physical properties. Of course, both the outer peripheral side front end portion 5b and the inner peripheral side base portion 5a may satisfy the rubber physical properties. When the bead filler has a two-layer structure, the inner peripheral side base portion 5a does not necessarily satisfy the above rubber physical properties, but preferably a rubber having a modulus larger than that of the outer peripheral side tip portion 5b is from the viewpoint of stability in handling. Is preferable.

  At least the outer peripheral side tip of the bead filler and the reinforcing rubber layer satisfy the above rubber characteristics, and both may be the same type of rubber or different types of rubber. However, it is preferable to use the same type of rubber, which can improve not only the run-flat durability but also the productivity.

  The tan δ and dynamic elastic modulus E1 used for specifying the physical properties of rubber in the present invention are physical properties when the rubber temperature is 60 ° C., and the measurement conditions are an initial strain of 10%, an amplitude of ± 2%, and a vibration frequency of 20 Hz. Means the measured value when.

  As described above, since the rubber property of at least the outer peripheral side tip of the bead filler is set to the low tan δ similar to that of the reinforcing rubber layer, heat generation at the upper end of the bead filler can be suppressed during run-flat running. The period until the sidewall near the upper end is damaged can be extended. Moreover, since the dynamic elastic modulus of the reinforcing rubber layer and the bead filler is in the range of 5 to 15 MPa without disposing the reinforcing fiber layer other than the carcass layer, it is possible to suppress the deterioration of ride comfort and road noise. . Moreover, rolling resistance can also be reduced by setting the bead filler and the reinforcing rubber layer to low tan δ.

  If tan δ of the bead filler and the reinforcing rubber layer is larger than 0.15, heat generation at the upper end of the bead filler increases during run flat running, and the run flat durability intended by the present invention cannot be obtained. On the other hand, when the dynamic elastic modulus is smaller than 5 MPa, the longitudinal rigidity of the sidewall portion becomes too low, and the steering stability is lowered. Further, the vehicle support function is lowered during run-flat running.

  In addition, when the dynamic elastic modulus is larger than 15 MPa, the vertical rigidity of the sidewall portion is increased, so that a problem peculiar to a run flat tire that the ride comfort is inferior to that of a normal tire becomes apparent.

  It is desirable for the bead filler and the reinforcing rubber layer to minimize the difference in rigidity between the two while keeping the dynamic elastic modulus E1 within the set range. When the dynamic elastic modulus of the bead filler is E1b and the dynamic elastic modulus of the reinforcing rubber layer is E1r, the ratio E1b / E1r to the former is in the range of 0.8 to 1.2. Since the dynamic elastic moduli E1b and E1r of the two are brought close to each other in this way, stress concentration on the tip of the bead filler is alleviated and run-flat durability can be further improved. is there.

  The thickness of the reinforcing rubber layer (thickness in the meridian section) is preferably 10 to 12 mm at the maximum thickness. If it is less than 10 mm, the run-flat running property may be unstable, and if it is larger than 12 mm, heat is easily generated, which is disadvantageous for durability.

  The pneumatic tire of the present invention is used as a side-reinforced run-flat tire, and is particularly suitable when applied to a tire having a flatness ratio of 55% or less.

  The tire physical properties are 225 / 50R17, the tire structure is shown in FIG. 1, the carcass layer is a two-ply rayon cord layer, and the maximum thickness of the reinforcing rubber layer is 12 mm. E1r) and 15 types of pneumatic tires for run-flat (Examples 1-6, Comparative Examples 1-9) with different rubber properties (tan δ and dynamic elastic modulus E1b) as shown in Table 1 did.

  Further, in Example 1, a comparative run-flat pneumatic tire (Comparative Example 10) having the same configuration as that of Example 1 except that a nylon fiber reinforcing layer was disposed outside the bead filler was manufactured.

  With respect to the above 16 types of tires, run-flat durability, riding comfort, road noise and rolling resistance were measured by the following test methods, and the results are shown in Table 1.

  From the test results shown in Table 1, the pneumatic tires of the present invention (Examples 1 to 6) all have run-flat durability without sacrificing riding comfort, road noise, and rolling resistance as compared with the comparative tires. It can be seen that the performance is improved.

[Run-flat durability]
A rim-assembled tire was mounted on the front right side of a domestic passenger car with an internal pressure of 0, and the vehicle was run on a test course at a speed of 90 km / h.

  Evaluation was shown by the index | exponent which sets the measured value of the comparative example 1 to 100. FIG. The larger the index value, the better the run flat durability.

[Ride comfort]
The rim-assembled tire was filled with air pressure of 230 kPa and mounted on a domestic passenger car, and the ride comfort when a specialized panelist traveled the test course was evaluated by a feeling test.

  Evaluation was shown by the index | exponent which sets the measured value of the comparative example 1 to 100. FIG. A larger index value means superior ride comfort.

[Road noise]
The rim-assembled tire was filled with air pressure of 230 kPa and mounted on a domestic passenger car. The tire was run on a paved road at a speed of 60 km / h, and the sound pressure level of the noise collected by a microphone attached to the position near the driver's window was measured.

  The evaluation was performed by using the reciprocal of the measured value, and indicated by an index with the reciprocal of the measured value of Comparative Example 1 being 100. A larger index value means better road noise.

[Rolling resistance]
Using a drum testing machine having a drum diameter of 1707 mm, the rolling resistance was measured under conditions of an air pressure of 230 kPa, a load of 5 kN, and a speed of 80 km / h.

  The evaluation was performed by using the reciprocal of the measured value, and indicated by an index with the reciprocal of the measured value of Comparative Example 1 being 100. The larger the index value, the better the rolling resistance.

1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is meridian sectional drawing of the pneumatic tire which consists of other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread 2 Side wall part 3 Bead part 4 Bead core 5 Bead filler 5a Base part 5b Tip part 6 Reinforcement rubber layer 7 Carcass layer 8 Belt layer

Claims (6)

  In a run-flat pneumatic tire in which a bead filler is disposed in each of a pair of left and right bead parts, and a crescent-shaped reinforcing rubber layer partially overlapping with the bead filler is disposed in a side wall part, the periphery of the bead filler Without arranging a reinforcing fiber layer other than the carcass layer, the rubber properties of at least the outer peripheral tip of the bead filler and the reinforcing rubber layer are tan δ of 0.15 or less, and the dynamic elastic modulus E1 is 5 or less. A pneumatic tire designed to be 15 MPa.   2. The pneumatic tire according to claim 1, wherein a ratio E1b / E1r of a dynamic elastic modulus E1b of at least an outer peripheral end portion of the bead filler to a dynamic elastic modulus E1r of the reinforcing rubber layer is set to 0.8 to 1.2. .   The pneumatic tire according to claim 1 or 2, wherein at least the outer peripheral end portion of the bead filler and the reinforcing rubber layer are the same type of rubber.   The pneumatic tire according to any one of claims 1 to 3, wherein the reinforcing rubber layer has a maximum thickness of 10 to 12 mm.   5. The bead filler according to any one of claims 1 to 4, wherein the bead filler has a two-layer structure of an inner peripheral base and an outer peripheral tip, and the outer peripheral tip satisfies the rubber characteristics of the tan δ and the dynamic elastic modulus E1. Pneumatic tire described in 2. The pneumatic tire according to any one of claims 1 to 5, wherein the flatness of the tire is 55% or less.

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