JP5098457B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having run-flat running performance, and more particularly, to improve braking / driving performance on ice during run-flat running while maintaining steering stability on snow during normal running. It relates to a pneumatic tire that is made possible.

  In some pneumatic tires, a reinforcing rubber layer having a crescent-shaped cross section is provided in a sidewall portion, and run flat running is possible based on the rigidity of the reinforcing rubber layer (for example, Patent Document 1 and Patent Document 2). reference).

  Such a side reinforcing type run flat tire supports the load based on the rigidity of the reinforcing rubber layer of the side wall portion. Therefore, when the run flat running, the tread portion T is buckled as shown in FIG. The contact area decreases, and the braking / driving performance when traveling on a low friction road surface tends to be reduced. In particular, in a tire designed so that the rigidity of the tread portion becomes low, such as a pneumatic tire for an icy and snowy road, this tendency appears remarkably, and the tire may idle on ice.

  As a countermeasure, a belt additional layer having a larger cord angle with respect to the tire circumferential direction is arranged on the outer peripheral side of the two belt layers embedded in the tread portion to increase the compression rigidity in the width direction of the tread portion. It has been proposed to suppress the buckling phenomenon of the part (see, for example, Patent Document 3).

However, when the rigidity of the tread part is extremely increased, the buckling phenomenon of the tread part is suppressed, but there is a problem that the steering stability on the snow during the normal running without puncture is lowered.
JP 2003-94912 A JP 2003-326924 A International Publication WO2003-024727 Pamphlet

  An object of the present invention is to provide a pneumatic tire that can improve braking / driving performance on ice during run-flat running while maintaining steering stability on snow during normal running.

The pneumatic tire of the present invention for achieving the above object is a pneumatic tire in which a reinforcing rubber layer having a crescent-shaped cross section is disposed on each of a pair of left and right sidewall portions,
Three belt layers are provided on the outer circumferential side of the carcass layer in the tread portion, the cord angle of the innermost belt layer with respect to the tire circumferential direction is set to 15 ° to 35 °, and the intermediate belt layer adjacent to the outer circumferential side thereof with respect to the tire circumferential direction The cord angle is 50 ° or more, and the cord angle with respect to the tire circumferential direction of the outermost belt layer adjacent to the outer peripheral side is 35 ° to 70 °,
Alternatively, three belt layers are provided on the outer circumferential side of the carcass layer in the tread portion, the cord angle of the innermost belt layer with respect to the tire circumferential direction is 50 ° to 75 °, and the tire circumference of the intermediate belt layer adjacent to the outer circumferential side thereof The cord angle with respect to the direction is 35 ° or less, the cord angle with respect to the tire circumferential direction of the outermost belt layer adjacent to the outer peripheral side is 50 ° to 75 °, and the cord angle of the innermost belt layer is the cord angle of the outermost belt layer. Has a larger structure,
And 0kPa pneumatic remove the valve core in a state assembled with the tire in a normal rim, when multiplied by the normal load, the maximum width of the non-contact region formed in the maximum width W and the ground in the region of the contact region of the tread portion The ratio w / W to w is 0.6 to 0.9 , and the ratio of the contact length L at the center position in the tire width direction of the contact area to the contact length l at the center position in the tire width direction of the non-contact area. l / L is 0.3 to 0.6 .

  In the present invention, in the side-reinforced run-flat tire, the dimensional relationship between the grounding region and the non-grounding region when the air pressure is 0 kPa is defined as described above, so that the braking / driving performance on ice is improved. While ensuring the limited necessary ground contact area, the rigidity in the width direction of the tread portion can be optimized and the steering stability on the snow during normal running can be maintained well. In particular, the ratio l / L of the contact length L at the center position in the tire width direction of the contact area to the contact length l at the center position in the tire width direction of the non-contact area is preferably 0.3 to 0.6. As a result, the relationship between the contact area and the rigidity of the tread portion is optimized, and the handling stability on snow during normal running and the braking / driving performance on ice during run-flat running can be achieved at a higher level. .

  In order to satisfy the dimensional relationship between the grounding area and the non-grounding area, the following belt structure can be employed. In other words, three belt layers are provided on the outer circumferential side of the carcass layer in the tread portion, the cord angle of the innermost belt layer with respect to the tire circumferential direction is set to 15 ° to 35 °, and the tire circumference of the intermediate belt layer adjacent to the outer circumferential side thereof is set. The cord angle with respect to the direction is preferably 50 ° or more, and the cord angle with respect to the tire circumferential direction of the outermost belt layer adjacent to the outer peripheral side is preferably 35 ° to 70 °. Alternatively, three belt layers are provided on the outer circumferential side of the carcass layer in the tread portion, the cord angle of the innermost belt layer with respect to the tire circumferential direction is 50 ° to 75 °, and the tire circumference of the intermediate belt layer adjacent to the outer circumferential side thereof The cord angle with respect to the direction is 35 ° or less, the cord angle with respect to the tire circumferential direction of the outermost belt layer adjacent to the outer peripheral side is 50 ° to 75 °, and the cord angle of the innermost belt layer is the cord angle of the outermost belt layer. It is preferable to make it larger.

  The present invention can be applied to various pneumatic tires, but particularly when applied to a pneumatic tire for ice and snowy roads in which a plurality of sipes are provided on a plurality of land portions divided into tread portions. It has a remarkable effect.

  In the present invention, the “regular rim” is a rim determined for each tire in the standard on which the tire is based, for example, “standard rim” for JATMA, “Measuring Rim” for ETRTO, and “TRAIN” for TRA. “Design Rim”. The “regular load” is a maximum value of the load capacity determined for each tire in the standard based on the tire. When the tire is a passenger car, the load is equivalent to 88% of the maximum load capacity.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a meridian half sectional view showing a pneumatic tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. Two carcass layers 4 are mounted between the pair of left and right bead portions 3 and 3, and end portions of the carcass layers 4 are folded around the bead core 5 from the inside to the outside of the tire. A bead filler 6 having a triangular cross section is disposed on the outer peripheral side of the bead core 5. Further, a reinforcing rubber layer 7 having a crescent-shaped cross section is disposed on each of the pair of left and right sidewall portions 2 and 2. The reinforcing rubber layer 7 is harder than the other rubber layers of the sidewall portion 2 and supports the load during run-flat travel based on its rigidity.

  On the other hand, on the outer peripheral side of the carcass layer 4 in the tread portion 1, three belt layers 8a, 8b, and 8c are arranged over the entire circumference of the tire. These belt layers 8a to 8c include reinforcing cords that are inclined with respect to the tire circumferential direction. Further, a belt cover layer 9 is disposed on the outer peripheral side of the belt layers 8a to 8c. The belt cover layer 9 includes a reinforcing cord oriented in the tire circumferential direction, and the reinforcing cord is continuously wound in the tire circumferential direction.

  FIG. 2 shows the ground contact shape of the pneumatic tire according to the embodiment of the present invention. That is, when the pneumatic tire is assembled to the regular rim, the valve core is pulled out, the air pressure is set to 0 kPa, and a normal load is applied, so that the ground contact shape of the tread portion 1 is formed as shown in FIG. At this time, the ratio w / W between the maximum width W of the grounding area A1 of the tread portion 1 and the maximum width w of the non-grounding area A2 formed in the grounding area A1 is 0.6 to 0.9, more preferably 0.7-0.8. The maximum width W of the contact area A1 and the maximum width w of the non-contact area A2 are dimensions measured in the tire width direction. Further, the ratio l / L of the contact length L at the center position C in the tire width direction of the contact area A1 and the contact length l at the center position C in the tire width direction of the non-contact area A2 is 0.3 to 0.6. Preferably, it becomes 0.35-0.45. The ground contact length L of the ground contact area A1 and the ground contact length l of the non-ground contact area A2 are each measured in a direction orthogonal to the tire width direction.

  In the side-reinforced run-flat tire configured as described above, the dimensional relationship between the ground contact area A1 and the non-ground contact area A2 when the air pressure is set to 0 kPa is defined as described above. While maintaining steering stability, braking / driving performance on ice during run-flat running can be improved. Here, if the ratio w / W is less than 0.6, the effect of improving the steering stability on the snow during normal running becomes insufficient. Conversely, if the ratio w / W exceeds 0.9, the effect on the ice during run-flat running is insufficient. The improvement effect of braking / driving performance becomes insufficient. Also, if the ratio l / L is less than 0.3, the effect of improving the steering stability on snow during normal driving will be insufficient, and conversely if it exceeds 0.6, the control on ice during run flat driving will be insufficient. The driving performance improvement effect is insufficient.

  FIG. 3 is a plan view showing a specific example of a tread portion and a belt layer in the pneumatic tire according to the embodiment of the present invention. 3, the tread portion 1 is provided with a plurality of vertical grooves 11 extending in the tire circumferential direction and a plurality of horizontal grooves 12 extending in the tire width direction. The vertical grooves 11 and the horizontal grooves 12 form a plurality of blocks. The land portion 13 is partitioned. A plurality of sipes 14 are formed in each of the land portions 13. This tread pattern is a suitable pattern as a pneumatic tire for icy and snowy roads.

  Among the three belt layers 8a to 8c embedded in the tread portion 1, the cord angle α1 with respect to the tire circumferential direction of the innermost belt layer 8a is set in the range of 15 ° to 35 °, and the middle adjacent to the outer peripheral side The cord angle β1 with respect to the tire circumferential direction of the belt layer 8b is set to 50 ° or more, and the cord angle γ1 with respect to the tire circumferential direction of the outermost belt layer 8c adjacent to the outer circumferential side thereof is set to a range of 35 ° to 70 °. Yes. In particular, the innermost belt layer 8a and the intermediate belt layer 8b are arranged so that the inclination directions of the cords with respect to the tire circumferential direction are opposite to each other, and the intermediate belt layer 8b and the outermost belt layer 8c are cords with respect to the tire circumferential direction. It is desirable to arrange so that the inclination directions are the same as each other.

  Thus, by setting the cord angle α1 of the innermost belt layer 8a, the cord angle β1 of the intermediate belt layer 8b, and the cord angle γ1 of the outermost belt layer 8c within the above ranges, the circumferential surface of the entire belt layer is set. The balance between the outer rigidity and the out-of-plane rigidity in the width direction is optimized, and as a result, the dimensional relationship between the grounding area A1 and the non-grounding area A2 in the tread portion 1 can be achieved. Here, if the cord angles α1, β1, and γ1 are out of the above range, a desired grounding shape cannot be obtained.

  FIG. 4 is a plan view showing another specific example of the tread portion and the belt layer in the pneumatic tire according to the embodiment of the present invention. In FIG. 4, the tread portion 1 is provided with a plurality of vertical grooves 11 extending in the tire circumferential direction and a plurality of horizontal grooves 12 extending in the tire width direction. The vertical grooves 11 and the horizontal grooves 12 form a plurality of blocks. The land portion 13 is partitioned. A plurality of sipes 14 are formed in each of the land portions 13. This tread pattern is a suitable pattern as a pneumatic tire for icy and snowy roads.

  Among the three belt layers 8a to 8c embedded in the tread portion 1, the cord angle α2 with respect to the tire circumferential direction of the innermost belt layer 8a is set in the range of 50 ° to 75 °, and the middle adjacent to the outer circumferential side The cord angle β2 with respect to the tire circumferential direction of the belt layer 8b is set to 35 ° or less, and the cord angle γ2 with respect to the tire circumferential direction of the outermost belt layer 8c adjacent to the outer circumferential side thereof is set to a range of 50 ° to 75 °. Yes. In particular, the innermost belt layer 8a and the intermediate belt layer 8b are arranged so that the inclination directions of the cords with respect to the tire circumferential direction are opposite to each other, and the intermediate belt layer 8b and the outermost belt layer 8c are cords with respect to the tire circumferential direction. It is desirable to arrange so that the inclination directions are the same as each other.

  Thus, by setting the cord angle α2 of the innermost belt layer 8a, the cord angle β2 of the intermediate belt layer 8b, and the cord angle γ2 of the outermost belt layer 8c within the above ranges, the circumferential surface of the entire belt layer is set. The balance between the outer rigidity and the out-of-plane rigidity in the width direction is optimized, and as a result, the dimensional relationship between the grounding area A1 and the non-grounding area A2 in the tread portion 1 can be achieved. Here, if the cord angles α2, β2, and γ2 are out of the above range, a desired grounding shape cannot be obtained.

  In each embodiment mentioned above, the kind of reinforcement cord of belt layers 8a-8c is not specifically limited, Aramid fiber cord, polyketone fiber cord, polyethylene naphthalate fiber cord, polyparaphenylene benzobis, besides steel cord A highly elastic organic fiber cord such as an oxazole fiber cord can be used.

  The pneumatic tire for snowy and snowy roads is characterized in that a plurality of sipes 14 are provided in each of a plurality of land portions 13 partitioned into a tread portion 1, and further, a cap tread constituting the tread portion 1. A soft rubber is used as the rubber. More specifically, rubber having a hardness of 40 to 55 is used as the cap tread rubber. The hardness referred to here is the durometer hardness (A) defined in JIS K6253.

  In the pneumatic tire for icy and snowy roads configured in this way, buckling is likely to occur in the tread portion 1 during run-flat running, so the dimensional relationship between the ground contact area A1 and the non-ground contact area A2 in the tread section 1 is defined as described above. By doing so, it is extremely meaningful to achieve both the steering stability on snow during normal running and the braking / driving performance on ice during run-flat running.

  In a pneumatic tire for icy and snowy roads with a tire size of 205 / 55R16 and a pair of left and right sidewall portions each provided with a crescent-shaped reinforcing rubber layer, the valve core is removed and the air pressure is 0 kPa with the tire assembled to a regular rim. As a ratio w / W between the maximum width W of the ground contact area of the tread portion when the normal load is applied and the maximum width w of the non-ground area formed in the ground contact area, and the center position in the tire width direction of the ground contact area The tires of the conventional examples, Examples 1 to 5 and Comparative Examples 1 to 4 in which the ratio 1 / L of the contact length L between the contact length L and the contact length l at the center position in the tire width direction of the non-contact area is set as shown in Table 1 Produced.

  For these test tires, the steering stability on snow during normal running and the driving performance on ice during run-flat running were evaluated by the following methods. The results are shown in Table 1.

Steering stability on snow:
Test tires mounted on wheels of rim size 16 × 7J and mounted on all wheels of a 2000cc rear-wheel drive vehicle. Front wheel air pressure is 220 kPa, rear wheel air pressure is 250 kPa. Sensory evaluation with a test driver was performed. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability on the snow during normal driving.

Driving performance on ice:
Attach the test tire to a wheel with a rim size of 16 × 7J and install it on all wheels of a 2000cc rear wheel drive car, pull out the valve core of one front wheel to make the air pressure 0 kPa, and make the air pressure of the other front wheel 220 kPa, It was confirmed whether or not the tire with the air pressure of the rear wheel set to 250 kPa and the air pressure set to 0 kPa when slipping at a low speed rotates without slipping. The evaluation results are indicated by “◯” when the tire rotates without slipping, and by “x” when the tire idles.

  As shown in Table 1, the tires of Examples 1 to 5 are driven on ice during run-flat running while maintaining sufficient steering stability on snow during normal running in comparison with the conventional example. The performance could be improved. On the other hand, the tires of Comparative Examples 1 and 3 had good driving performance on ice during run-flat travel, but had insufficient steering stability on snow during normal travel. Further, although the tires of Comparative Examples 2 and 4 have good steering stability on snow during normal running, the driving performance on ice during run-flat running was insufficient.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is a top view which shows the contact shape of the pneumatic tire which consists of embodiment of this invention. It is a top view which shows the specific example of the tread part and belt layer in the pneumatic tire which consists of embodiment of this invention. It is a top view which shows the other specific example of the tread part and belt layer in the pneumatic tire which consists of embodiment of this invention. It is sectional drawing for demonstrating the deformation | transformation condition of the tread part at the time of run flat running of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Reinforcement rubber layer 8a, 8b, 8c Belt layer 9 Belt cover layer A1 Grounding area A2 Non-grounding area

Claims (5)

In a pneumatic tire in which a reinforcing rubber layer having a crescent-shaped cross section is disposed on each of a pair of left and right sidewall portions,
Three belt layers are provided on the outer circumferential side of the carcass layer in the tread portion, the cord angle of the innermost belt layer with respect to the tire circumferential direction is set to 15 ° to 35 °, and the intermediate belt layer adjacent to the outer circumferential side thereof with respect to the tire circumferential direction The cord angle is 50 ° or more, and the cord angle with respect to the tire circumferential direction of the outermost belt layer adjacent to the outer peripheral side is 35 ° to 70 ° ,
When the tire is assembled to a regular rim, the valve core is pulled out, the air pressure is set to 0 kPa, and when a regular load is applied, the maximum width W of the grounding area of the tread portion and the maximum width of the non-grounding area formed in the grounding area The ratio w / W to w is 0.6 to 0.9, and the ratio of the contact length L at the center position in the tire width direction of the contact area to the contact length l at the center position in the tire width direction of the non-contact area. A pneumatic tire, wherein l / L is 0.3 to 0.6 . In a pneumatic tire in which a reinforcing rubber layer having a crescent-shaped cross section is disposed on each of a pair of left and right sidewall portions,
Three belt layers are provided on the outer circumferential side of the carcass layer in the tread portion, the cord angle of the innermost belt layer with respect to the tire circumferential direction is set to 50 ° to 75 °, and the intermediate belt layer adjacent to the outer circumferential side thereof with respect to the tire circumferential direction. The cord angle is 35 ° or less, the cord angle with respect to the tire circumferential direction of the outermost belt layer adjacent to the outer peripheral side is 50 ° to 75 °, and the cord angle of the innermost belt layer is larger than the cord angle of the outermost belt layer Has a larger structure,
When the tire is assembled to a regular rim, the valve core is pulled out, the air pressure is set to 0 kPa, and when a regular load is applied, the maximum width W of the grounding area of the tread portion and the maximum width of the non-grounding area formed in the grounding area The ratio w / W to w is 0.6 to 0.9, and the ratio of the contact length L at the center position in the tire width direction of the contact area to the contact length l at the center position in the tire width direction of the non-contact area. A pneumatic tire, wherein l / L is 0.3 to 0.6 . The innermost belt layer and the intermediate belt layer are arranged such that the inclination directions of the cord with respect to the tire circumferential direction are opposite to each other, and the intermediate belt layer and the outermost belt layer are inclined with respect to the tire circumferential direction. The pneumatic tire according to claim 1, wherein the tires are arranged so that the directions are the same. The innermost belt layer and the intermediate belt layer are arranged such that the inclination directions of the cord with respect to the tire circumferential direction are opposite to each other, and the intermediate belt layer and the outermost belt layer are inclined with respect to the tire circumferential direction. The pneumatic tire according to claim 2, wherein the tires are arranged so that the directions are the same.   The pneumatic tire for icy and snowy roads according to any one of claims 1 to 4, wherein a plurality of sipes are provided on each of a plurality of land portions divided into tread portions.

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