JP5145646B2 - Run flat tire - Google Patents

Description

  The present invention relates to a run-flat tire, and more particularly, to a run-flat tire that improves durability during puncturing while improving riding comfort and steering stability during non-puncturing.

  2. Description of the Related Art Conventionally, as a run flat tire that can safely travel a fixed distance even after puncturing, a tire rubber having a crescent-shaped hard rubber layer disposed on a tire sidewall is widely known. In this type of run-flat tire, when the tire is punctured and becomes zero pressure, a crescent-shaped hard rubber layer disposed on the sidewall portion runs while supporting the load of the vehicle.

  However, since this type of run-flat tire supports the vehicle load with the hard rubber on both the left and right sides as described above, the center portion in the width direction of the tread portion 4 buckles as illustrated in FIG. Since the grounding is performed so that the region up to the upper side of the sidewall portion 3 is caught, there is a problem in that the rubber in the upper region of the sidewall portion 3 generates heat and breaks down.

  As a countermeasure, a tie element composed of a large number of cords substantially orthogonal to the tire equatorial plane is disposed on the outer peripheral side of the two belt layers disposed in the tread portion to increase the compression rigidity in the width direction in the tread portion. Thus, there is a proposal for suppressing the buckling phenomenon (see Patent Document 1).

However, in this proposal, since the tie element is arranged on the grounding side of the two belt layers, the tread rigidity is significantly increased, and the load dependency of the cornering power is reduced. There was a problem that riding comfort and handling stability (particularly, lane change performance) during puncture running were reduced.
JP-A-6-191243

  An object of the present invention is to solve the above-described conventional problems, and to improve the riding comfort and handling stability during non-puncturing while simultaneously improving the durability during puncturing. It is to provide a flat tire.

In order to achieve the above object, a run flat tire according to the present invention has a carcass layer mounted between a pair of left and right bead portions, and a hard rubber having a substantially crescent cross-sectional shape inside the tire of the carcass layer in a sidewall portion. In a run flat tire having at least two belt layers in which a cord direction is crossed between layers on the outer peripheral side of the carcass layer in the tread portion, a cord angle with respect to the tire circumferential direction is between the belt layers. The gist of the invention is that a belt reinforcement layer that is substantially 90 ° is disposed and that the belt reinforcement layer is divided into a plurality of parts in the tire width direction .

  According to the present invention, the belt reinforcing layer having a cord angle of substantially 90 ° with respect to the tire circumferential direction is disposed between at least two belt layers intersecting with each other in the cord direction. By securing the out-of-plane rigidity in the width direction of the entire belt layer while suppressing the increase, it is possible to improve riding comfort and handling stability during non-puncturing and to improve run-flat durability.

Furthermore, since the movement of the tread part during puncturing is reduced, it becomes possible to reduce the burden on the side wall part. Therefore, by reducing the hard rubber layer arranged on the side wall part, the weight can be reduced. While being planned, it is possible to further improve the riding comfort during non-puncture traveling.
Moreover, in the present invention, since the belt reinforcing layer is divided into a plurality of portions in the tire width direction, the balance between the out-of-plane rigidity in the circumferential direction and the out-of-plane rigidity in the width direction is optimized as the entire belt layer. In addition, it is possible to improve the riding comfort and handling stability during non-puncturing and the durability during puncturing in a well-balanced manner.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
Figure 1 is a cross-sectional view, cross-sectional view showing a tread portion of a pneumatic tire according to the implementation form of FIG. 2 according to the present invention showing the outline of air-filled tire of the present invention.

  In FIG. 1, the run flat tire 1 includes a pair of left and right bead portions 2, 2, sidewall portions 3, 3 extending radially outward from the bead portions 2, 2, and radial directions of the sidewall portions 3, 3. And a cylindrical tread portion 4 that connects the outer sides.

  A carcass layer 5 is mounted between the pair of left and right bead portions 2, 2, and a hard rubber layer 6 having a substantially crescent-shaped cross section is disposed inside the carcass layer 5 in the sidewall portion 3, and a tread portion 4, belt layers 7 and 8 of at least two layers (two layers in the figure) in which the cord directions intersect each other are disposed on the outer peripheral side of the carcass layer 5.

  Between the two belt layers 7 and 8, a belt reinforcing layer 9 having a cord angle with respect to the tire circumferential direction of substantially 90 ° is disposed. Steel cords or high-strength and high-modulus organic fiber cords are used as the cords constituting the belt layers 7 and 8 and the belt reinforcing layer 9. Further, the cord angle of the cord constituting the belt reinforcing layer 9 with respect to the tire circumferential direction is set to 90 °, but a fluctuation range of ± 10 ° is allowed. In the figure, reference numeral 10 denotes a belt cover layer made of an organic fiber cord such as nylon extending in the tire circumferential direction for suppressing the diameter expansion of the belt layers 7 and 8 during high-speed running, depending on the required characteristics of the tire. May not be placed. The belt cover layer 10 may be disposed so as to cover the entire width of the belt layers 7 and 8.

  In the run-flat tire 1 configured as described above, the belt reinforcing layer 9 having a cord angle of substantially 90 ° with respect to the tire circumferential direction is disposed between the belt layers 7 and 8, so that the tread rigidity is extremely low. By securing the out-of-plane rigidity in the width direction of the entire belt layer while suppressing the increase, it is possible to improve riding comfort and handling stability during non-puncturing and to improve run-flat durability.

  Furthermore, since the movement of the tread portion 4 during puncturing is reduced, the burden on the sidewall portion 3 can be reduced. Therefore, by reducing the hard rubber layer 6 disposed on the sidewall portion 3, The ride comfort during non-puncturing can be further improved while reducing the weight.

In the Figure 1, the case of arranging the belt layers 7 and 8 of the outer peripheral side into two layers of the carcass layer 5 in the tread portion 4, the number of belt layers disposed in the tread portion 4 is limited to There is nothing. Even when three or more belt layers are disposed, the above-described belt reinforcing layer 9 may be disposed between at least two of the belt layers.

Further, in FIG. 1, but the belt reinforcing layer 9 disposed between the two layers belt layer 7 and 8 show the case which is constituted by the form of a continuous single piece to the tire width direction, the run-flat of the present invention In the tire 1, as shown in FIG. 2 , the belt reinforcing layer 9 is divided into a plurality (two in the drawing, 9 a and 9 b) in the tire width direction . This optimizes the balance between the out-of-plane rigidity in the circumferential direction and the out-of-plane rigidity in the width direction as the entire belt layer, and the riding comfort and handling stability during non-puncturing and durability during puncturing Can be improved in a balanced manner.

  In the present invention, the width W3 of the belt reinforcing layer 9 disposed between the two belt layers 7 and 8 may be set to 30 to 80%, preferably 35 to 75% of the maximum belt width W1. If the width W3 of the belt reinforcing layer 9 is less than 30% of the belt maximum width W1, the effect of suppressing buckling at the time of puncturing cannot be sufficiently obtained, and the effect of improving the run-flat durability is insufficient. The effect of improving riding comfort during non-puncture driving cannot be obtained sufficiently.

In the run flat tire 1 of the present invention shown in FIG. 2 , the width W3 of the belt reinforcing layer 9 is the sum of the widths of the divided belt reinforcing layers 9 (9a and 9b in FIG. 2) (Wa + Wb in FIG. 2). ) Applies.

  The belt reinforcing layer 9 in the present invention is preferably arranged so that the ends 9e, 9e on the tire shoulder Sh side are located inside the ends 8e, 8e of the belt layer 8 having the minimum width in the tire width direction. Thereby, the separation of the belt layer 8 in the vicinity of the terminals 8e and 8e can be suppressed, and the deterioration of the durability of the belt portion 4 can be prevented.

  In the case described above, an interval of 5 mm or more, preferably 10 mm or more may be provided between the terminal 9 e of the belt reinforcing layer 9 and the terminal 8 e of the belt layer 8 having the minimum width. Furthermore, when the belt reinforcing layer 9 is divided into two in the tire width direction as in the embodiment of FIG. 2, the interval Wo between the left and right belt reinforcing layers 9a, 9b is set to 1/2 of the belt maximum width W1. It is good to adjust so that it may become an interval of a grade. Thereby, the outstanding buckling suppression effect at the time of puncture driving | running can be ensured, without receiving the influence of the position of the main groove formed in the tread part 4, a tread pattern, etc.

  As described above, the cords constituting the belt layers 7 and 8 and the belt reinforcing layer 9 in the run-flat tire 1 of the present invention are constituted by steel cords, and from the viewpoint of weight reduction, have high strength and high elastic modulus. Organic fiber cord is used. Examples of the high-strength and high-modulus organic fiber cord include an aramid fiber, a polyketone fiber, a polyethylene naphthalate fiber, a polyparaphenylene benzobisoxazole fiber, or a composite fiber containing these. However, as the most preferable mode, a steel cord may be used as the cord constituting the belt reinforcing layer 9 from the viewpoint of ensuring the buckling suppressing effect during puncture traveling.

  Further, when steel cords are used for the belt layers 7 and 8 and the belt reinforcing layer 9, the wire diameters of the steel cords constituting the belt layers 7 and 8 are set to the wire diameters of the steel cords constituting the belt reinforcing layer 9. It is preferable to make the diameter larger. More preferably, the strand diameter of the steel cord constituting the belt reinforcing layer 9 is adjusted to be 1.1 to 1.3 times the strand diameter of the steel cord constituting the belt layers 7 and 8. As a result, the run-flat durability can be reliably improved while substantially maintaining the rideability during non-puncture traveling.

  That is, the run-flat durability can be improved by increasing the wire diameter of the steel cord constituting the belt reinforcing layer 9 and reducing the number of wires of the steel cord to equalize the amount of wire used. Further, the steel cord constituting the belt reinforcing layer 9 is made thicker, and the weight can be reduced by reducing the number of wires of the steel cord and the amount of wire used to equalize the rigidity.

  If the above-mentioned value is less than 1.1 times, it becomes difficult to secure the out-of-plane rigidity in the width direction as the entire belt layer, so the effect of improving the run-flat durability is reduced. Since the out-of-plane rigidity in the width direction becomes too high, the effect of improving riding comfort during non-puncture traveling tends to decrease.

  In the run-flat tire 1 of the present invention, the movement of the tread portion 4 during puncture traveling is reduced, so that the burden on the sidewall portion 3 can be reduced. Therefore, it is possible to reduce the form of the hard rubber layer 6 disposed on the sidewall portion 3 to reduce the weight and improve the rideability during non-puncturing.

  That is, in the run flat tire 1 of the present invention, the hard rubber layer 6 is set to a height H in the tire radial direction of 50 to 90%, preferably 60 to 85% of the tire cross-section height SH. The thickness of 6 can be reduced. As a guideline for reducing the thickness of the hard rubber layer 6, the ratio H / D between the height H of the hard rubber layer 6 in the tire radial direction and the maximum thickness D in the tire width direction may be adjusted to 8-20. .

  As a result, it is possible to reliably improve rideability during non-puncturing while substantially maintaining run-flat durability. Therefore, in particular, when emphasis is placed on rideability at the time of non-puncture traveling, the above-described H / D value may be adjusted to 8-20. If the H / D is less than 8, the thickness of the hard rubber layer 6 is too large, which is contrary to the weight reduction and the effect of improving riding comfort is reduced. If the H / D exceeds 20, the hard rubber layer 6 is hard. The thickness of the rubber layer 6 becomes too thin, and the effect of improving the run-flat durability is reduced.

As described above, in the run-flat tire of the present invention, the belt reinforcing layer having a cord angle with respect to the tire circumferential direction of substantially 90 ° is disposed between the two belt layers in which the cord directions intersect each other. At the same time, the belt reinforcement layer is divided into a plurality of portions in the tire width direction, thereby improving the riding comfort and handling stability during non-puncturing and improving the durability during puncturing. In particular, the present invention is preferably applied to a studless tire that is designed to have low tread rigidity in order to improve running performance particularly on icy and snowy road surfaces.

The tire size (225 / 45R17), the specification of the belt reinforcement layer and the tire structure (Fig. 1) excluding the position of the belt reinforcement layer are used in common, the material of the cord constituting the belt reinforcement layer, the angle with respect to the tire circumferential direction, the belt reinforcement layer form, the conventional tire (conventional example) having different as position, width and table 1, respectively, ratio, the the belt maximum width of the width, compared tires (Comparative examples 1 and 2) and the present invention tires (example 1 -5 ) were produced.

  In each tire, the cord of the belt layer is a steel cord, and the steel cord constituting the belt layer and the belt reinforcing layer and the number of driving thereof are the same (structure: 1 × 6, strand diameter: 0.25 mm, number of driving) : 38 pieces / 50 mm), and the tensile strength of the aramid cord of the belt reinforcing layer in Example 6 was made equal to the tensile strength of the steel cord of the belt layer. Further, the height H in the tire radial direction of the hard rubber layer disposed in the sidewall portion was 75 mm, and the maximum thickness D in the tire width direction was 10.7 mm.

  These eight types of tires were evaluated for ride comfort and handling stability during non-puncture driving and durability during puncture driving (hereinafter referred to as run-flat durability) using the test methods shown below. This is also shown in Table 1.

[Ride comfort]
Each tire is mounted on a rim (17 x 8 JJ), filled with air pressure of 200 kPa, mounted on the front and rear wheels of a 2500cc rear-wheel drive vehicle, and a test course consisting of flat and irregular road surfaces is averaged at 50km / h The vehicle was run at / h, and sensory evaluation was performed by three test drivers. The result was displayed by the index | exponent which sets the prior art example to 100. The larger the value, the better the riding comfort.

[Maneuvering stability]
The above-mentioned vehicle is run on a test course consisting of a flat circuit surface at a speed of 80 to 250 km / h, and three test drivers from the viewpoints of steering performance during lane change and cornering and stability during straight running The sensory evaluation was performed. The results were combined and displayed as an index with the conventional example being 100 as an evaluation of steering stability. The larger the value, the better the steering stability.

[Run-flat durability]
Of the tires mounted on the vehicle described above, the air pressure on the right side of the rear wheel was set to zero (0 kPa), and the elliptical course was run counterclockwise at an average speed of 90 km / h. The test driver felt abnormal noise due to tire failure and measured the distance traveled until he stopped driving, and the result was displayed as an index with the conventional example as 100. The larger the value, the better the run flat durability.

From Table 1, it can be seen that the tires of the present invention ( Examples 3, 4, and 5 ) have improved ride comfort and handling stability while improving run-flat durability as compared with conventional tires. In the tires of the present invention ( Examples 1 and 2 ), the run-flat durability was slightly decreased, but it was confirmed that this level of decrease was an acceptable level. Further, in the comparative tire (Comparative Example 2) , since the cord angle of the belt reinforcing layer is inclined in the tire circumferential direction, the effect of improving riding comfort and driving stability is not sufficiently obtained as compared with the conventional tire. In addition, it was confirmed that the run-flat durability did not reach the acceptable level. The comparative tire (Comparative Example 1) has improved run-flat durability, riding comfort, and handling stability compared to the conventional tire. Excluded from the tires of the present invention because it did not reach Examples 1-5).

An overview of the sky pneumatic tire of the present invention is a cross-sectional view showing. It is a partial cross-sectional view showing a tread portion of a pneumatic tire according to the implementation embodiments of the present invention. It is sectional drawing explaining the deformation | transformation condition of the tread part at the time of the puncture driving | running | working of the conventional run flat tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Run flat tire 2 Bead part 3 Side wall part 4 Tread part 5 Carcass layer 6 Hard rubber layer 7, 8 Belt layer 9 Belt auxiliary layer 10 Belt cover layer

Claims (7)

A carcass layer is mounted between a pair of left and right bead portions, a hard rubber layer having a substantially crescent cross-sectional shape is disposed inside the tire of the carcass layer in the sidewall portion, and the outer peripheral side of the carcass layer in the tread portion In the run flat tire having at least two belt layers in which the cord directions are crossed between the layers,
A run-flat tire in which a belt reinforcing layer having a cord angle with respect to the tire circumferential direction of substantially 90 ° is disposed between the belt layers, and the belt reinforcing layer is divided into a plurality of portions in the tire width direction . The run flat tire according to claim 1, wherein a width of the belt reinforcing layer is 30 to 80% of a maximum width of the belt layer. 3. The run-flat tire according to claim 1, wherein a tire shoulder side end of the belt reinforcing layer is located on an inner side in a tire width direction than an end of the belt layer having the smallest width of the belt layers. The run-flat tire according to claim 3, wherein the tire shoulder side terminal is located 5 mm or more on the inner side in the tire width direction than the terminal of the belt layer having the minimum width. The run flat tire according to any one of claims 1 to 4, wherein the cord constituting the belt layer and the belt reinforcing layer is a steel cord. The run-flat tire according to claim 5, wherein a strand diameter of a steel cord constituting the belt reinforcing layer is 1.1 to 1.3 times a strand diameter of a steel cord constituting the belt layer. The run flat tire according to any one of claims 1 to 6 , wherein a ratio H / D between a height H in the tire radial direction of the hard rubber layer and a maximum thickness D in the tire width direction is 8 to 20.

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