JP4661260B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire suitable for use under severe driving conditions such as circuit driving, and more particularly to a pneumatic tire that improves uneven wear resistance and steering stability.

  Generally, a pneumatic tire has a plurality of main grooves extending in the tire circumferential direction on a tread surface, and a land portion composed of ribs and block rows is divided by these main grooves. In such a pneumatic tire, under a use condition that generates a large turning force such as circuit running, the ground pressure is concentrated on the edge portion of the land portion outside the vehicle, and the portion tends to be worn heavily. Moreover, due to the reaction force when the edge portion outside the vehicle is deformed, the other portions of the land portion are lifted or slipped, and the turning force tends to decrease. And these tendencies become more prominent in the tread surface on the vehicle outer side.

As a countermeasure, it has been proposed to form a chamfered portion at an edge portion of the land portion outside the vehicle (see, for example, Patent Document 1). When the chamfered portion is provided on the edge portion of the land portion outside the vehicle, the deformation reaction force of the land portion is suppressed, the effective ground contact area is increased, and the effect of improving uneven wear resistance and steering stability is obtained. However, in the above proposal, since the length of the chamfered portion in the tire axial direction is constant throughout the tread surface, the grounding property is poor under severe driving conditions such as circuit driving, and uneven wear resistance and steering stability are insufficient. is there.
JP-A-6-24213

  An object of the present invention is to provide a pneumatic tire that is suitable for use under severe driving conditions such as circuit driving and that is excellent in uneven wear resistance and steering stability.

The pneumatic tire of the present invention for achieving the above Symbol purpose, the tread surface, the groove extending to at least two tire circumferential direction, a pneumatic tire having a land portion of a plurality of rows partitioned by these grooves, A chamfered portion is provided at an edge portion on the vehicle outer side of the land portion, the width of the _Nth chamfered portion counted from the vehicle outer side is W _N, and the edge portion provided with the Nth chamfered portion from the vehicle outer ground contact end. The distance is L _N , the width of the circumferential groove adjacent to the Nth chamfer is GW _N, and the average width of the circumferential groove completely included in the range of 70% of the vehicle outside of the ground contact width is GW _ave When the width of the circumferential groove adjacent to the chamfered portion is different from each other at least in the range of 70% of the vehicle outer side of the ground contact width, the chamfered portion formed on the edge portion on the vehicle outer side is represented by the following formula ( 1 ) It is intended.
W _N = (− α × L _N + β) × (GW _N / GW _ave ) ( 1 )
However, the slope α is an arbitrary constant selected from the range of 0.03 ≦ α ≦ 0.06, and the intercept β is an arbitrary constant selected from the range of 6 ≦ β ≦ 8.

  Here, the contact width is the contact width when a pneumatic pressure specified by JATMA is filled and a mass corresponding to 88% of the load capacity is loaded perpendicularly to the tread surface.

In the present invention, a chamfered portion is provided on the vehicle outer side of the edge portion of the land portion, the more deformation is larger vehicle outer side to increase the width W _N of the chamfer during turning, and according to the distance L _N from the vehicle outer ground contact edge chamfering Since the width W _N of the portion is changed, the contact pressure concentration at the outer edge portion of the vehicle is more effectively mitigated, and uneven wear resistance is improved. In addition, since the reaction force when the edge portion outside the vehicle is deformed is more effectively suppressed, the land portion on the opposite side to the chamfered portion comes into good contact with the ground. As a result, the ground contact area is increased and the steering stability is improved. Therefore, even when used under severe driving conditions such as circuit driving, excellent uneven wear resistance and steering stability can be exhibited. Further, by correcting the width W _N of the chamfered portion according to the width GW _N of the circumferential groove adjacent to the chamfer, it is possible to further improve the steering stability and uneven wear resistance.

In the present invention, the width GW _N of the circumferential groove adjacent to the chamfered portion is preferably 3 mm ≦ GW _N ≦ 18 mm. The depth d of the chamfered portion is preferably 4% to 20% of the depth D of the adjacent groove.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention, FIG. 2 shows an outline of a tread surface in a tire meridian section, and FIG. 3 shows an outline of a main groove in a tire meridian section. is there. As shown in FIG. 1, five main grooves 2 extending in the tire circumferential direction and a plurality of lug grooves 3 extending in the tire width direction are formed on the tread surface 1, and these main grooves 2 and lug grooves 3 are formed. A plurality of rows of block-like or rib-like land portions 4 are divided. Accordingly, a pneumatic tire is configured in which the tread pattern is asymmetric on both sides of the tire equator line and the mounting direction of the tire front and back with respect to the vehicle is specified.

In the pneumatic tire, a chamfered portion 5 is formed at an edge portion on the vehicle outer side of the land portion 4 divided by the main groove 2. Here, the width of the N-th chamfered portion 5 counted from the outside of the vehicle is W _N , the distance from the vehicle outer grounding end of the edge portion provided with the N-th chamfered portion 5 is L _N, and the Nth When the width of the circumferential groove 2 adjacent to the chamfered portion 5 is GW _N and the average width of the circumferential groove 2 completely included in the range of 70% outside the ground width TCW is GW _ave , at least grounding In the range of 70% of the vehicle outer side with the width TCW, the chamfered portion 5 formed at the edge portion on the outer side of the vehicle satisfies the relationship of the following expression (1).
W _N = (− α × L _N + β) × (GW _N / GW _ave ) (1)
However, the slope α is an arbitrary constant selected from the range of 0.03 ≦ α ≦ 0.06, and the intercept β is an arbitrary constant selected from the range of 6 ≦ β ≦ 8.

That is, as shown in FIGS. 1 and 2, the width of the chamfered portion 5 is W ₁ , W ₂ , W ₃ , W ₄ , W _{5 in} order from the outside of the vehicle, and the distance of the edge portion of the land portion 4 on the outside of the vehicle is set. L _N is set to L ₁ , L ₂ , L ₃ , L ₄ and L _{5 in} order from the outside of the vehicle, and the width of the groove 2 is set to GW ₁ , GW ₂ , GW ₃ , GW ₄ and GW _{5 in} order from the outside of the vehicle . when given a certain relationship between the distance L ₁ ~L ₅ of width W ₁ to _W-5 and the edge portion of the chamfer 5 Rutotomoni, width W ₁ to _W-5 of the chamfer 5 of the groove 2 Correction is performed based on the widths GW _{1 to} GW ₅ . The slope α and the intercept β are obtained based on experiments. If these constants are out of the above range, it is difficult to improve the ground contact property under severe driving conditions. As shown in FIG. 3, the width W _N of the chamfered portion 5 is a length measured in the tire axial direction of a portion where the land portion 4 is chamfered (a portion indicated by a broken line).

In this way, the chamfered portion 5 is provided at the vehicle outer edge portion of the land portion 4 divided by the groove 2, and the width of the chamfered portion 5 is increased toward the vehicle outer side which is largely deformed when turning, and the distance from the vehicle outer ground contact end is increased. By changing the width W _N of the chamfered portion 5 according to L _N , the contact pressure concentration at the edge portion on the vehicle outer side of the land portion 4 can be effectively relieved, and uneven wear resistance can be improved. Further, the reaction force when the vehicle outer side of the edge portion of the land portion 4 is deformed to effectively suppress, as a result, it is possible to improve the steering stability by improving the grounding property. Thereby, even if it is a case where it uses in severe driving | running | working conditions, such as circuit driving | running | working, the outstanding uneven wear resistance and steering stability can be exhibited. Furthermore, since the width W _{N of the} chamfered portion is corrected in accordance with the width GW _N of the circumferential groove 2 adjacent to the chamfered portion 5, it is possible to further improve uneven wear resistance and steering stability. . The width GW _N (see FIG. 3) of the circumferential groove 2 adjacent to the chamfered portion 5 is defined in the range of 3 mm ≦ GW _N ≦ 1 mm.

  Note that in a pneumatic tire in which the orientation of the tire front and back with respect to the vehicle is specified, the vehicle inner portion of the tread surface 1 is not effectively grounded during turning. Therefore, it suffices if the above relationship is satisfied at least in the range of 70% outside the vehicle with the ground contact width TCW. Moreover, you may satisfy the said relationship about the pneumatic tire in which the mounting direction of the tire front and back with respect to a vehicle is not designated.

  The depth d of the chamfered portion 5 is set in the range of 4% to 20% of the depth D of the adjacent groove 2 as shown in FIG. When the depth d of the chamfered portion 5 is less than 4% of the depth D of the main groove 2, the contact pressure is concentrated on the edge portion, and uneven wear resistance is deteriorated, and steering stability is also deteriorated. On the other hand, when the depth d of the chamfered portion 5 exceeds 20% of the depth D of the groove 2, the grounding performance is impaired, and the steering stability is lowered.

In a pneumatic tire of tire size 225 / 45R17, a symmetrical tread design having five main grooves extending in the tire circumferential direction is formed on the tread surface as shown in FIG. 1, and the land portions divided by these main grooves are formed. a chamfered portion is provided on the edge portion of the vehicle outer side, a large tire of reference examples 1-3 and example 1 as the vehicle outside were produced respectively based on the above equation (2) the width W ₁ to _W-5 of the chamfer .

For comparison, a tire of the conventional example in which the width W ₁ to _W-5 of the chamfer constant relationship width W ₁ to _W-5 on to what is larger as the vehicle outside-type chamfer (1) are satisfied No comparative examples 1 and 2 were produced respectively.

These test tires were evaluated for steering stability and uneven wear resistance by the following test methods, and the results are shown in Table 1. In Table 1, the average width GW _ave of the circumferential groove completely included in the range of 70% outside the vehicle of the ground contact width TCW is an average value of GW _{1 to} GW ₃ .

Steering stability:
Each test tire was assembled on a wheel with a rim size of 17 × 8 JJ, filled with an air pressure of 230 kPa and mounted on an automobile with a displacement of 2000 cc, and an actual vehicle sensory test was conducted by running five laps continuously on the circuit. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability.

Uneven wear resistance:
Each test tire was assembled on a wheel with a rim size of 17 × 8 JJ, filled with an air pressure of 230 kPa and mounted on an automobile having a displacement of 2000 cc, and continuously run for 5 laps on a circuit, and the appearance of the tire after running was visually evaluated. The evaluation results are shown by a 5-point method in which the conventional example is 3. The larger this value, the better the uneven wear resistance.

The As can be seen from Table 1, the tires of Example 1 was able to significantly improve the steering stability and uneven wear resistance as compared with the slave come example. The tires of Comparative Examples 1 and 2 were insufficient, although an improvement effect of steering stability and uneven wear resistance was observed.

FIG. 2 is a development view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention. It shows a contour of the tire meridian cross section of the tread surface of the pneumatic tire according to an embodiment of the present invention. It shows a contour of the tire meridian cross section of the main groove formed on the tread surface of the pneumatic tire according to an embodiment of the present invention.

1 tread surface 2 main groove 3 lug groove 4 land portion 5 chamfered portion d depth of chamfered portion D depth of main groove W _N width of chamfered portion L distance of edge portion having _N chamfered portion from vehicle ground contact edge TCW Grounding width

Claims (3)

In the pneumatic tire having at least two grooves extending in the tire circumferential direction on the tread surface and a plurality of rows of land portions partitioned by the grooves, a chamfered portion is provided at an edge portion on the vehicle outer side of the land portion. the width of the N-th chamfer a W _N, counting from the outside, the distance from the vehicle outer grounding end of the edge portion with the N-th chamfer as L _N, adjacent to the N-th chamfer peripheral When the width of the groove in the direction is GW _N and the average width of the groove in the circumferential direction that is completely included in the range of 70% outside the ground width is GW _ave , at least in the range of 70% outside the vehicle in the ground width, A pneumatic tire in which circumferential groove widths adjacent to the chamfered portions are different from each other, and the chamfered portions formed on the outer edge of the vehicle satisfy the relationship of the following formula ( 1 ).
W _N = (− α × L _N + β) × (GW _N / GW _ave ) ( 1 )
However, the slope α is an arbitrary constant selected from the range of 0.03 ≦ α ≦ 0.06, and the intercept β is an arbitrary constant selected from the range of 6 ≦ β ≦ 8. The pneumatic tire according to claim 1 , wherein a width GW _N of a circumferential groove adjacent to the chamfered portion is 3 mm ≦ GW _N ≦ 18 mm. Depth d of the chamfer, the pneumatic tire according to any one of 4% to 20% of the depth D of the adjacent grooves claims 1-2.

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