JP6228034B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  Conventionally, various pneumatic tires have been proposed for the purpose of improving braking performance on a wet road surface (hereinafter referred to as “wet brake performance”). For example, Patent Document 1 has a plurality of circumferential main grooves provided within the width of the contact surface of the tread, and the tread rubber constituting the tread has a temperature of 0 ° C., a frequency of 52 Hz, an initial strain of 2.0%, dynamic motion. Tan δ under the condition of 1.0% strain is 0.90 or more, 60 ° C., frequency 52 Hz, initial strain 2.0%. It is disclosed that tan δ under the condition of a dynamic strain rate of 1.0% is 0.12 or less and the negative rate within the contact width of the tread is 20 to 40%.

Japanese Unexamined Patent Publication No. 2014-8910

  However, the demand for wet brake performance is increasing year by year, and there is room for further improvement in wet brake performance even in the technique of Patent Document 1.

  An object of the present invention is to solve the above-described problems and to provide a pneumatic tire capable of improving wet brake performance.

The pneumatic tire according to the present invention is the pneumatic tire having one or more circumferential grooves extending continuously in the tire circumferential direction on the tread surface, and the total groove width of the circumferential grooves is 0.19 of the tread width. The negative rate of the tread tread is 28 to 32%, and the tread rubber forming the tread tread has a temperature of 0 ° C., a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1%. The loss tangent tan δ under the conditions is 0.89 or more, and the dynamic storage elastic modulus E ′ of the tread rubber under the conditions of temperature 30 ° C., frequency 52 Hz, initial strain 2%, dynamic strain 1% is 4.6. It is -8.2MPa.
According to the pneumatic tire of the present invention, the wet brake performance can be improved.

In the pneumatic tire of the present invention, the total groove width of the circumferential grooves is 0.20 to 0.22 times the tread width, and the negative rate of the tread surface is 29 to 30%. The dynamic storage elastic modulus E ′ of the tread rubber under the conditions of a temperature of 30 ° C., a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1% is preferably 5.0 to 7.0 MPa.
Thereby, wet brake performance can further be improved.

  According to the present invention, it is possible to provide a pneumatic tire that can improve wet brake performance.

It is a tire width direction sectional view of one embodiment of the pneumatic tire of the present invention. It is an expanded view of the tread pattern of one embodiment of the pneumatic tire of the present invention.

  FIG. 1 and FIG. 2 show an embodiment of the pneumatic tire of the present invention (hereinafter sometimes simply referred to as “tire”). In addition, although the tire demonstrated by this embodiment is comprised as a pneumatic radial tire for passenger cars, this invention is applicable also to another kind of pneumatic tire.

  In general, in order to improve wet brake performance, ensure sufficient drainage performance, ensure sufficient ground contact area during tire rolling, and tire and road surface during tire rolling. It is necessary to apply a sufficient frictional force during this period. If any one of these is not achieved, the wet brake performance cannot be sufficiently improved. The tire of this embodiment improves wet brake performance by ensuring all of drainage performance, ground contact area, and frictional force.

FIG. 1 shows a cross section of the tire along the tire width direction at the position of line AA in FIG. As shown in FIG. 1, the tire according to the present embodiment includes a tread portion 20, a pair of sidewall portions 21 that continuously extend radially outward from the tread portion 20 in the tire width direction, and each sidewall portion 21. A pair of continuous bead portions 22 is provided on the inner side in the tire radial direction. Further, the tire extends in a toroidal shape between the pair of bead portions 22, and includes a carcass 23 composed of one or more carcass plies including a radial arrangement code, and a tire radial direction outer side than a crown portion of the carcass 23. A belt 24 composed of one or more belt plies, a tread rubber 25 provided outside the belt 24 in the tire radial direction, and a bead core 26 embedded in the bead portion 22 are provided. An outer surface of the tread rubber 25 forms a tread surface 1.
However, in the tire of the present invention, the internal structure of the tire is not limited to that shown in FIG. 1, and any tire can be used.

As shown in FIG. 2, the tread tread 1 has one or more (three in the illustrated example) circumferential grooves 2 a to 2 c (hereinafter collectively “circumferential direction”) that continuously extend along the tire circumferential direction. Groove 2 ”is sometimes formed.
Here, the “tread surface 1” refers to the road surface when the tire that is assembled to the applicable rim and filled with the specified internal pressure is rolled with a load corresponding to the maximum load capacity applied. Means the outer peripheral surface of the entire circumference of the tire.
“Applicable rim” is an industrial standard effective in the area where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) JATMA YEAR BOOK, and in Europe, ETRTO (The European Tire and Rim). STANDARDDS MANUAL of Technical Organization, TRA (The Tire and Rim Association, Inc.) YEAR BOOK, etc. in the United States, etc. Rim). The “specified internal pressure” means the air pressure corresponding to the maximum load capacity in the applicable size / ply rating described in the above JATMA YEAR BOOK etc., and the “maximum load capacity” The maximum mass allowed to be loaded.
In the example of the figure, the circumferential grooves 2a to 2c extend in parallel with the tire circumferential direction, but the circumferential grooves 2a to 2c may extend in a substantially zigzag shape.

In the example shown in FIG. 2, one of the three circumferential grooves 2 (circumferential groove 2b) extends on the tire equatorial plane CL, and two (circumferential grooves 2a and 2c) serve as the tire equatorial plane. It extends on both sides of the CL in the tire width direction. The three circumferential grooves 2 divide four rows of land portions 11a to 11d (hereinafter sometimes collectively referred to as “land portions 11”) extending in the tire circumferential direction. Among the four rows of land portions 11a to 11d, the two rows of land portions between the circumferential grooves 2 are the center land portions 11b and 11c, and the two rows of land portions outside the tire width direction from these. Are shoulder land portions 11a and 11d.
In the example of the figure, the center land portions 11b and 11c have one end opened in the circumferential grooves 2a and 2c adjacent to the center land portions 11b and 11c and the outer side in the tire width direction, and gradually grooved toward the inner side in the tire width direction. As the width becomes narrower, the other end terminates in the center land portions 11b and 11c, and the outer notch groove 3 and one end open into the circumferential groove 2b on the tire equatorial plane CL, and as it goes outward in the tire width direction. An inner notch groove 4 is provided in which the groove width gradually decreases and the other end terminates in the center land portions 11b and 11c. The outer notch groove 3 and the inner notch groove 4 are connected by a sipe 5. Furthermore, between the pair of sipes 5 adjacent to each other in the tire circumferential direction, one end of each of the center land portions 11b and 11c is formed in the circumferential grooves 2a and 2c adjacent to the center land portions 11b and 11c and outside in the tire width direction. A sipe 6 is provided that is open and has the other end terminating in the center land portions 11b and 11c.
In the example of the figure, the shoulder land portions 11a and 11d have one end opened to the circumferential grooves 2a and 2c adjacent to the shoulder land portions 11a and 11d and the tire width direction inner side, and the tread tread surface 1 ends in the tire width direction (hereinafter referred to as the tread tread surface 1). , Referred to as “tread end”.) A widthwise groove 7 extending outward in the tire width direction across the TE, and disposed outside the widthwise groove 7 in the tire width direction and bent convexly to one side of the tire circumferential direction. A V-shaped groove 8 is provided. Further, the shoulder land portions 11a and 11d extend from the innermost end in the tire width direction of the V-shaped groove 8 to the inner side in the tire width direction and terminate in the shoulder land portions 11a and 11d, and in the tire circumferential direction. A sipe 10 that extends along the tire circumferential direction and ends in the shoulder land portions 11a and 11d is provided between a pair of widthwise grooves 7 adjacent to each other.
However, in the tire of the present invention, the tread pattern is not limited to that shown in FIG.

In the present invention, the total groove width of the circumferential groove 2, that is, the total of the groove width W1 of the circumferential groove 2a, the groove width W2 of the circumferential groove 2b, and the groove width W3 of the circumferential groove 2c (W1 + W2 + W3) is 0.19 to 0.23 times the tread width TW, and the negative rate of the tread surface 1 is 28 to 32%.
Here, the tread width TW is a width measured in the tire width direction along the tread tread surface 1 with the tire mounted on the applied rim, filled with the specified internal pressure, and in an unloaded state between the tread ends TE. It is.

  Further, the “groove width” of the circumferential groove 2 refers to a width of the circumferential groove 2 measured in the direction perpendicular to the groove width center line (in the example of the figure, the tire width direction) in the tread surface 1. . The “negative rate of the tread tread 1” refers to the ratio of the area of the tread tread 1 that does not contact the ground to the total tread tread 1 area. “A portion of the tread tread 1 that does not come into contact with the ground” includes various grooves in the tread tread 1. The groove width and the negative rate are values measured along the tread tread surface 1 with the tire mounted on the applied rim, filled with the specified internal pressure, and no load.

Setting the negative rate of the tread tread 1 as described above leads to an improvement in drainage, as well as ensuring the rigidity of the land part, and consequently, the reduction of the contact area due to the fall of the land part at the time of tire load rolling. It leads to suppression. On the other hand, when the negative rate is lower than 28%, sufficient drainage performance cannot be obtained, and when the negative rate is higher than 32%, sufficient land portion rigidity cannot be obtained, and tire rolling There is a risk of land collapse.
Furthermore, by setting the total groove width of the circumferential grooves 2 as described above, the circumferential groove 2 having the highest drainage capacity occupies most of the portion of the tread surface 1 that does not contact the ground. In addition, the drainage can be sufficiently increased and the land portion rigidity can be sufficiently ensured. On the other hand, when the ratio of the total groove width of the circumferential groove 2 to the tread width TW is lower than 0.19, sufficient drainage cannot be obtained, and the groove width of the circumferential groove 2 with respect to the tread width TW If the total ratio is higher than 0.23, sufficient land portion rigidity cannot be obtained.

  From the same viewpoint, the total groove width (W1 + W2 + W3) of the circumferential groove 2 is preferably 0.20 to 0.22 times the tread width TW. Moreover, it is preferable that the negative rate of the tread surface 1 is 29 to 30%.

Furthermore, in the present invention, the loss tangent tan δ of the tread rubber 25 under the conditions of temperature 0 ° C., frequency 52 Hz, initial strain 2%, dynamic strain 1% is 0.89 or more, and the tread rubber 25 has a temperature 30 ° C. The dynamic storage elastic modulus E ′ under the conditions of a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1% is 4.6 to 8.2 MPa.
In the present invention, the loss tangent tan δ (the ratio (E ″ / E ′) between the dynamic loss elastic modulus E ″ and the dynamic storage elastic modulus E ′) and the dynamic storage elastic modulus E ′ are the dynamic tensile viscoelasticity. The value obtained by putting the test piece of the vulcanized rubber which comprises tread rubber 25 on each of the above-mentioned conditions using a measuring test machine is pointed out.

By setting the loss tangent tan δ of the tread rubber 25 as described above, the frictional force acting between the tread tread surface 1 and the road surface during load rolling of the tire can be sufficiently increased, leading to an increase in braking force. . On the other hand, when the loss tangent tan δ is lower than 0.89, sufficient frictional force cannot be obtained between the tire and the road surface during load rolling, and sufficient braking force cannot be obtained.
Further, setting the dynamic storage elastic modulus E ′ of the tread rubber 25 as described above leads to optimization of the rigidity of the tread rubber 25, so that the tread rubber 25 can easily follow the road surface when the tire rolls. Become. On the other hand, when the dynamic storage elastic modulus E ′ is lower than 4.6 MPa, the rigidity of the land portion becomes too low, and the land portion may fall down when the tire rolls, and the dynamic storage elastic modulus E ′ is When the pressure is higher than 8.2 MPa, the land portion rigidity becomes too high, and the tread rubber 25 may not be able to sufficiently capture the road surface when the tire is rolling.

  From the same viewpoint, the dynamic storage elastic modulus E ′ of the tread rubber 25 under the conditions of a temperature of 30 ° C., a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1% is preferably 5.0 to 7.0 MPa. . Further, the loss tangent tan δ of the tread rubber 25 under the conditions of a temperature of 0 ° C., a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1% is preferably 0.890 or more.

  Further, from the viewpoint of reducing rolling resistance, the loss tangent tan δ of the tread rubber 25 under the conditions of a temperature of 60 ° C., a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1% is 0.122 to 0.166. preferable.

  As described above, according to the present embodiment, the groove width of the circumferential groove 2 related to the tread pattern and the negative rate of the tread tread 1 are optimized, and further, the loss tangent tan δ related to the physical properties of the tread rubber 25 and dynamic By optimizing the storage elastic modulus E ′, it is possible to improve the drainage performance, increase the contact area, and increase the frictional force, and the synergistic effect of these can improve the wet brake performance.

In order to confirm the effect of the present invention, tires of Examples 1 to 5 and Comparative Examples 1 to 8 were made as trial products. The specifications of each tire are shown in Table 1 below. Each of the tires of Examples 1 to 5 and Comparative Examples 1 to 8 has a tire size of 195 / 65R15 and has a tread pattern similar to that shown in FIG.
In Table 1, “(W1 + W2 + W3) / TW” refers to the ratio of the total groove width of the circumferential grooves 2a to 2c to the tread width TW, and “negative rate” refers to the negative of the tread tread 1 “Tan δ” refers to the loss tangent of the tread rubber 25 under the conditions of a temperature of 0 ° C., a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1%, and “E ′” represents the tread rubber 25 The dynamic storage elastic modulus under the conditions of a temperature of 30 ° C., a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1%. These measurement conditions are as described above.

And each tire was assembled | attached to the rim | limb of 6J, and the wet brake performance was evaluated, The result is shown in Table 1.
The wet brake performance test was conducted in accordance with the EU regulation Wet Grip grading test method (draft) (TEST METHOD FOR TIRE WET GRIP GRADING (C1 TYRES)), and the wet brake performance of each tire was expressed as a relative index. A larger index value means better wet brake performance.

  As can be seen from Table 1, the tires of Examples 1 to 5 had excellent wet brake performance as compared with the tires of Comparative Examples 1 to 8.

  1: tread surface 2, 2, 2a-2c: circumferential groove 3: outer notch groove 4: inner notch groove 5, 6, 9, 10: sipe, 7: width direction groove, 8: V-shaped groove 11: Land part, 11a, 11d: Shoulder land part, 11b, 11c: Center land part, 20: Tread part, 21: Side wall part, 22: Bead part, 23: Carcass, 24: Belt, 25: Tread rubber 26: Bead core, CL: Tire equatorial plane, TE: Tread end, TW: Tread width, W1 to W3: Groove width of circumferential groove

Claims (2)

In a pneumatic tire having one or more circumferential grooves extending continuously in a tire circumferential direction on a tread surface,
The total groove width of the circumferential grooves is 0.19 to 0.23 times the tread width,
The tread tread negative rate is 28-32%,
The loss tangent tan δ of the tread rubber forming the tread surface under the conditions of temperature 0 ° C., frequency 52 Hz, initial strain 2%, dynamic strain 1% is 0.89 or more,
The pneumatic tire according to claim 1, wherein the tread rubber has a dynamic storage elastic modulus E ′ of 4.6 to 8.2 MPa under conditions of a temperature of 30 ° C., a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1%. . The total groove width of the circumferential grooves is 0.20 to 0.22 times the tread width;
The negative rate of the tread tread is 29-30%,
2. The dynamic storage elastic modulus E ′ of the tread rubber 25 under conditions of a temperature of 30 ° C., a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1% is 5.0 to 7.0 MPa. Pneumatic tire.

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