JP5769750B2 - Pneumatic tire - Google Patents

Description

  In particular, the present invention relates to a pneumatic tire with improved handling stability while maintaining a limit grip.

  As passenger cars and heavy-duty vehicles become more sophisticated, tires attached to these vehicles are durable enough to withstand high-speed driving and driving on various road surfaces, limit grip performance and steering stability when turning the vehicle, etc. Is required.

  For example, in the pneumatic tire described in Patent Document 1, by providing a belt reinforcing layer (circumferential belt), an effect of suppressing protrusion in the tire radial direction due to centrifugal force accompanying rotation of the tire, so-called soot By providing a protective layer (belt in the width direction) on the outer side in the tire radial direction of this belt reinforcing layer, not only the tread circumferential direction but also the tread circumferential direction can be used for input to the tire. The durability of the reinforcing elements in the belt reinforcing layer is enhanced by dispersing. Therefore, the pneumatic tire has high durability.

International Publication No. 2009/093325

  According to the pneumatic tire described above, since the rigidity of the tread surface is increased, the lateral force acting on the tread surface is increased, and the limit grip performance of the tire can be improved.

  However, it has been found that in the pneumatic tire described above, when a slip angle is given to the tire, a sudden lateral force is generated particularly when the slip angle is in a minute range.

  Therefore, the present invention provides a pneumatic tire capable of improving steering stability by gently generating a lateral force when a minute slip angle is given while maintaining a limit grip property of the tire. For the purpose.

The gist of the present invention is as follows.
The pneumatic tire according to the present invention includes a spiral belt layer formed by rubber-coating a plurality of cords arranged in parallel to each other and extending in the tread circumferential direction on the tire tread, and positioned radially outward from the spiral belt layer. The pneumatic tire has a belt protective layer formed by rubber-covering a plurality of cords arranged in parallel to each other and extending in the tread width direction, and a tread rubber positioned outward in the tire radial direction of the belt protective layer. The thickness Deb of a tread rubber (hereinafter also referred to as “tread ground end-belt protective layer outermost end rubber”) positioned between the tread ground end and the outermost end in the tread width direction of the belt protective layer. The thickness Dbb of the tread rubber located between the outermost ends in the tread width direction of the belt protective layer (hereinafter also referred to as “rubber between the outermost ends of the belt protective layer”). Rather large, the spiral belt layer includes a spiral belt layer main portion extending across between the tread widthwise outermost end of the spiral belt layer, at least one of the end portions of the spiral belt layer, the tire radially inward Or a spiral belt layer folded portion folded outwardly in the tire radial direction from the outer side in the tread width direction toward the tire equatorial plane side, and the inner end in the tread width direction of the spiral belt layer folded portion is a belt protective layer Tread width direction outermost end and tread width direction outermost end of the belt protective layer and tread width direction inner end of the spiral belt layer folded portion as compared with the rubber thickness Deb. the thickness Dbt of the tread rubber located between the is characterized in large Ikoto.

With the above-described configuration, it is possible to improve the steering stability by increasing the rigidity of the tread and maintaining the limit grip property, and gently generating a lateral force when a minute slip angle is given.
“High limit grip performance (high)” means that the maximum lateral force generated when a slip angle is given to the tire is large.
In addition, “extending in the tread circumferential direction” does not mean strictly extending in a direction parallel to the tread circumferential direction, but also means extending by 0 ° to 10 ° with respect to the tread circumferential direction. To do. Further, “extending in the tread width direction” does not mean strictly extending in a direction parallel to the tread width direction, but also means extending at an inclination of 60 ° to 90 ° with respect to the tread circumferential direction. .
Furthermore, the “tread grounding end” refers to a flat plate when a pneumatic tire is mounted on an applicable rim, set to a predetermined air pressure, placed in a stationary state perpendicular to the flat plate, and a load corresponding to a predetermined mass is applied. It points out the tread width direction both ends in the contact surface. By the way, “applied rim” is an industrial standard effective in the area where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK, in Europe, ETRTO (European Tire and Rim Technical Organization). STANDARD MANUAL, in the United States, refers to a rim defined by TRA (THE TIRE and RIM ASSOCATION INC.) YEAR BOOK, etc. The “predetermined air pressure” refers to an air pressure (maximum air pressure) corresponding to a tire maximum load capacity of a standard such as JATMA in a tire of an applicable size. “Load corresponding to a predetermined mass” refers to the maximum tire load of the standard such as JATMA.
Furthermore, “rubber thickness” refers to the thickness in the tire radial direction. Moreover, the thickness of the tread rubber in a specific region refers to the average value of the rubber thickness in that region.

  According to the pneumatic tire of the present invention, it is possible to improve steering stability while maintaining the limit grip property.

It is a tire axial direction sectional view showing a tread of a tire of an example of the present invention.

Hereinafter, embodiments of the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view in the tire axial direction of a tread of a pneumatic tire according to an example of the present invention. The pneumatic tire 1 includes a tread 2, a pair of sidewall portions (not shown) extending inward in the tire radial direction from the side portion of the tread 2, and a pair extending inward in the tire radial direction from the sidewall portion. And a bead portion (not shown).

  The pneumatic tire 1 includes a spiral belt layer 3 formed by rubber-coating a plurality of cords arranged in parallel to each other on the tread 2 and extending in the circumferential direction of the tread. A belt protective layer 4 formed by rubber-covering a plurality of cords arranged parallel to each other and extending in the tread width direction, and the belt protective layer 4 positioned outside the tire radial direction. And tread rubber 5.

As shown in FIG. 1, the thickness of the tread rubber 5 located between the tread grounding end TG and the outermost end 4e in the tread width direction of the belt protective layer (in FIG. 1, 4e1 and 4e2, the same applies hereinafter), That is, the thickness of the tread rubber 5 located between the surface passing through the tread ground contact edge TG and parallel to the tire equator surface and the surface passing through the outermost end 4e in the tread width direction of the belt protective layer and parallel to the tire equator surface is set. Deb and the thickness of the tread rubber 5 positioned between the outermost ends 4e of the belt protective layer in the tread width direction, that is, the surface passing through the outermost end 4e1 of the belt protective layer in the tread width direction and parallel to the tire equatorial plane The thickness of the tread rubber positioned between the outermost end 4e2 in the tread width direction of the belt protective layer and the surface parallel to the tire equatorial plane is denoted by Dbb.
Here, in this pneumatic tire 1, it is required that Dbb> Deb.

  In the pneumatic tire 1, since the spiral belt layer 3 is provided, an effect of preventing protrusion in the tire radial direction during tire rotation, a so-called wrinkle effect, is obtained, and the rigidity of the tread is increased. Therefore, when a slip angle is given to the tire, the lateral force acting on the tread surface is increased, and the limit grip performance of the tire is improved.

  On the other hand, the tread rubber located on the outer side in the tire radial direction of the belt protective layer is strongly pressed between the spiral belt layer and the belt protective layer and the road surface, and the shear strain increases. Therefore, when a slip angle is given to the tire, a sudden lateral force is generated particularly when the slip angle is in a very small range.

  Here, in this pneumatic tire 1, the thickness of the tread rubber 5 in the region where the spiral belt layer 3 and the belt reinforcing layer 4 are stacked in the tire radial direction is not stacked between the spiral belt layer 3 and the belt reinforcing layer 4. By making it larger than the thickness of the tread rubber 5 in the region, the shear strain can be relaxed and the generation of lateral force can be moderated. Therefore, the steering stability of the tire can be improved.

Here, in the pneumatic tire 1, the thickness of the tread rubber 5 is not increased over the entire tread ground contact width Tw, but is particularly positioned between the outermost ends 4 e in the tread width direction of the belt protective layer. A tread rubber (hereinafter also referred to as “rubber between both outermost ends of the belt protective layer”) having a thickness Dbb between the tread grounding end TG and the outermost end 4e in the tread width direction of the belt protective layer. The thickness is made larger than the thickness Deb (hereinafter also referred to as “tread grounding end-belt protective layer outermost end rubber”). By adopting this configuration, it is possible to suppress a decrease in the rigidity of the tread and to secure a limit grip property.
The tread contact width refers to the maximum linear distance between the tread contact ends in the tire axial direction.

  Therefore, according to the pneumatic tire of the present invention, the rigidity of the tread is increased, the limit grip property is maintained, and the lateral force is gently generated when a small slip angle is given to improve the handling stability. Can be made.

Here, the shear strain generated in the rubber between the outermost ends of the belt protective layer is larger than the shear strain generated in the rubber between the tread ground end-belt protective layer and the outermost end. Further, the heat generated in the tread during tire rolling generally increases with the thickness of the tread rubber.
Therefore, by making Dbb larger than Deb, not only the shear strain is relaxed in the center region, the generation of lateral force is moderated, and the steering stability of the tire is improved, but also the shoulder region In this case, it is also possible to obtain an effect of suppressing heat generation of the tread rubber and suppressing deterioration of durability.

  Further, in the pneumatic tire 1, the rubber thickness Deb between the tread grounding end and the belt protective layer outermost end and the rubber thickness Dbb between the belt protective layer outermost ends are 1.1 ≦ Dbb / Deb ≦ It satisfies the relationship of 1.4.

  When Dbb / Deb ≧ 1.1, the above-described effect of ensuring the tire's limit grip property can be reliably obtained while improving the steering stability of the tire. Further, if Dbb / Deb ≦ 1.4, when Dbb / Deb> 1.4, the rigidity of the tread rubber is reduced due to the Dbb becoming too thick, and the steering stability is lowered. Problems such as a decrease in the limit grip property and a deterioration in heat resistance can be avoided.

  For the same reason, in this pneumatic tire 1, it is more preferable that Dbb / Deb satisfies the relationship of 1.2 ≦ Dbb / Deb ≦ 1.3.

  As described above, in the pneumatic tire of the present invention, Dbb / Deb is preferably 1.1 or more and 1.4 or less, and more preferably 1.2 or more and 1.3 or less.

Furthermore, in this pneumatic tire 1, the spiral belt layer 3 is composed of one spiral belt layer main body portion 3a and two spiral belt layer folded portions 3b sandwiching the spiral belt layer main body portion 3a.
Specifically, as shown in FIG. 1, the spiral belt layer body 3 a continuously extends from one side of the tread 2 in the tread width direction toward the other side. At both ends 3we of the spiral belt layer main body 3a in the tread width direction, both end portions 3ep of the spiral belt layer are directed from the inner side in the tire radial direction to the outer side in the tire radial direction and from the outer side in the tread width direction toward the tire equatorial plane side. Will be folded. At this time, in the pneumatic tire 1, the inner end 3 e in the tread width direction of the spiral belt layer folded portion is located on the inner side in the tread width direction than the outermost end 4 e in the tread width direction of the belt protective layer. Both ends 3ep of the folded spiral belt layer in the tread width direction are referred to as spiral belt layer folded portions 3b.

  In this pneumatic tire 1, two end portions 3ep of the spiral belt layer are folded back. However, in the pneumatic tire of the present invention, if at least one of both end portions of the spiral belt layer is folded back. Good. Further, in this pneumatic tire 1, both end portions 3ep of the spiral belt layer are folded outward in the tire radial direction, but in the pneumatic tire of the present invention, they may be folded back inward in the tire radial direction. .

  In this pneumatic tire 1, by folding the spiral belt layer 3 as described above, a region in which the spiral belt layer main body portion 3a and the spiral belt layer folded portion 3b are stacked in the tire radial direction is provided. Therefore, the wrinkle effect generated in the pneumatic tire 1 is further increased, and the durability of the tire can be further improved.

  Here, the thickness of the tread rubber located between the outermost end 4e in the tread width direction of the belt protective layer and the inner end 3e in the tread width direction of the spiral belt layer folded portion, that is, the outermost direction in the tread width direction of the belt protective layer. A tread rubber (hereinafter referred to as “belt protective layer outermost layer) located between a surface passing through the end 4e and parallel to the tire equator plane and a surface passing through the inner end 3e in the tread width direction of the spiral belt layer folded portion and parallel to the tire equator plane The thickness of the outer end-spiral folded-back portion inner end rubber is also referred to as Dbt. In this pneumatic tire 1, the thickness Deb of the rubber between the tread ground end and the outermost end of the belt protective layer and the thickness of the rubber between the outermost end of the belt protective layer and the inner end of the spiral folded portion are Dbt in FIG. As shown, the relationship Dbt> Deb is satisfied.

In this pneumatic tire 1, the spiral belt layer body portion 3 a and the spiral belt layer folded portion 3 b are arranged between the outermost end 4 e in the tread width direction of the belt protective layer and the inner end 3 e in the tread width direction of the spiral belt layer folded portion. The belt protective layer 4 is laminated in the tire radial direction. As a result, a region where the rigidity of the tread is extremely high is generated.
In the pneumatic tire 1, the thickness of the tread rubber 5 provided in this region is larger than the thickness of the tread rubber 5 in the region where the spiral belt layer 3 and the belt protective layer 4 are not laminated. The above effect of improving the steering stability by gently generating a lateral force when a small slip angle is given while maintaining the limit grip property can be obtained.
As described above, in the pneumatic tire of the present invention, it is preferable that Dbt> Deb.

Further, in the pneumatic tire 1, as shown in FIG. 1, a plurality of cords positioned inward in the tire radial direction from the spiral belt layer 3 and arranged in parallel to each other and extending obliquely in the tread circumferential direction are covered with rubber. A cross belt layer 8 composed of two belt layers 6 and 7 is formed.
Here, the belt layers 6 and 7 are provided such that the cord 6c and the cord 7c intersect each other, and form the intersecting belt layer 8. In particular, in the pneumatic tire 1, the cords 6c and 7c are treads. It is provided so that inclination directions are opposite to each other with respect to the circumferential direction.

  In the pneumatic tire 1, by providing the cross belt layer 8, the rigidity with respect to the input to the tire in the tread circumferential direction and the tread width direction is further increased.

If the cross belt layer 8 is provided, the rigidity of the tread is further increased. Therefore, the tread rubber positioned on the outer side in the tire radial direction of the spiral belt layer is more strongly pressed between the spiral belt layer and the road surface and sheared. Distortion is further increased. Therefore, it is possible to improve the steering stability by increasing the rigidity of the tread and maintaining the limit grip property, and generating a lateral force gently when a minute slip angle is given, thereby improving the steering stability. It is easy to get an effect.
As described above, the pneumatic tire of the present invention preferably has a cross belt layer.

  Further, in the pneumatic tire 1, a tread width direction distance L between the outermost end 4e in the tread width direction of the belt protective layer and the inner end 3e in the tread width direction of the spiral belt layer folded portion (L1 and L2 in FIG. 1). Is 10 mm to 30 mm.

If the distance is 10 mm or more, most of the tread portion can be covered with the belt protective layer, so the pressure of the belt protective layer generated between the spiral belt layer and the road surface is relieved, and the cord in the belt protective layer Can increase the durability. Further, if the distance is 30 mm or less, an increase in the tire radial thickness of the tread portion in the shoulder side region is suppressed, and an increase in heat generation in the tread portion during tire rolling (particularly during high speed running) is suppressed. Thus, a decrease in the durability of the tire can be suppressed.
The tread surface is the contact surface with the flat plate when a pneumatic tire is attached to the applicable rim, set to a predetermined air pressure, placed in a stationary state perpendicular to the flat plate, and a load corresponding to a predetermined mass is applied. Point to.

  For the same reason, in the pneumatic tire 1, the distance L is more preferably 15 mm to 20 mm.

  As described above, in the pneumatic tire of the present invention, the tread width direction distance between the outermost end in the tread width direction of the belt protective layer and the inner end in the tread width direction of the spiral belt layer folded portion is preferably 10 mm to 30 mm. More preferably, it is 15 mm to 20 mm.

  In the pneumatic tire 1 of an example of the present invention, the width Wsb in the tread width direction of the spiral belt layer 3 is preferably 90% to 100% of the tread ground contact width Tw. Further, the width Wbp in the tread width direction of the belt protective layer 4 is preferably 80% to 90% of the tread ground contact width Tw. Furthermore, the tread width direction distance Wtr between the tread width direction outermost end 3we of the spiral belt layer and the tread width direction inner end 3e of the spiral belt layer folded portion is preferably 15% to 35% of the tread grounding width Tw. .

  In the pneumatic tire 1 according to an example of the present invention, the cord 3c forming the spiral belt layer 3 may extend in a linear shape, a zigzag shape, a corrugated shape, or the like. Further, it can extend at a predetermined angle, for example, 0 ° to 5 ° with respect to the tread circumferential direction, and extend in a spiral shape in the tread width direction.

  Moreover, in this pneumatic tire 1, the cord 4c forming the belt protective layer 4 can be extended to have a shape such as a linear shape, a zigzag shape, and a wave shape.

Furthermore, in this pneumatic tire 1, the inclination angle θ1 of the cord 6c constituting the belt layer 6 of the intersecting belt layer 8 with respect to the tread circumferential direction and the cord 7c constituting the belt layer 7 of the intersecting belt layer 8 with respect to the tread circumferential direction. The inclination angle θ2 is not particularly limited, but is preferably 45 ° or more.
When θ1 and θ2 are set to 45 ° or more, the rigidity of the spiral belt layer can be complemented and the rigidity in the tread width direction can be increased. Here, θ1 and θ2 indicate the smaller angle of the angles formed by the extending direction of the cord and the tread circumferential direction.

  Examples of the cord used in the pneumatic tire of the present invention include organic fiber and steel. In particular, from the viewpoint of enhancing the durability of the tire, an organic fiber cord is preferable. Examples of the material for the organic fiber cord include aramid, nylon, and aromatic polyamide. In particular, aramid is preferably used in order to ensure high rigidity.

  This pneumatic tire 1 can be manufactured, for example, by extruding tread rubber using an extruder and changing the amount of rubber used when affixing to the raw tire in the tread width direction of the raw tire. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

  In this example, a pneumatic tire (245 / 40R18) for passenger cars was used. In Example 1, pneumatic tires having specifications shown in Table 1 were produced, and the following evaluations were performed using the tires. In Comparative Example 1, pneumatic tires having specifications shown in Table 1 were prepared, and the following evaluations were performed in the same manner as in Example 1 using the tires.

(Performance evaluation)
The produced pneumatic tire was mounted on an applicable rim (9.5 J × 18) defined in JATMA standard to produce a rim assembled pneumatic tire. The pneumatic tire was mounted on a vehicle under the conditions of an internal pressure of 230 kPa and a load of 4 kPa, and the following tests were performed.
In a flat belt type tester (manufactured by MTS), the pneumatic tire was run on a safety walk at a speed of 30 km / hour with a camber angle of 2 °. Then, the maximum generated lateral force (maximum generated cornering power) when the slip angle (cornering angle) is set to -7 ° to + 7 ° is measured, and the pneumatic tires at the following points (1) and (2) are measured. evaluated.

(1) Limit grip property About the maximum generated lateral force measured in the above test, an index that is a relative evaluation with the evaluation result of Comparative Example 1 as 100 was calculated. The evaluation results are shown in Table 1. The larger the index, the greater the maximum generated lateral force of the pneumatic tire and the better the limit grip property.
(2) Steering stability In a minute slip angle region (-1 ° to + 1 °), the inclination of the maximum generated lateral force measured in the above test with respect to the slip angle was calculated, and the evaluation result of Comparative Example 1 was set to 100. An index for relative evaluation was calculated. The evaluation results are shown in Table 1. The smaller the index, the slower the lateral force generation at a minute slip angle of the pneumatic tire, and the better the steering stability.

  According to the pneumatic tire of the present invention, it is possible to improve steering stability while maintaining the limit grip property.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 2 tread, 3 spiral belt layer, 3a spiral belt layer main-body part, 3b spiral belt layer folding | turning part, 3ep both ends of a spiral belt layer, 3e inner tread width direction end of a spiral belt layer folding part, 3we spiral Tread width direction ends of belt layer main body, 4 belt protective layer, 4e tread width direction outermost end of belt protective layer, 5 tread rubber, 6, 7 belt layer, 6c, 7c belt layer cord, 8 cross belt layer, CL tire equatorial plane, thickness of tread rubber located between tread width direction outermost ends of Dbb belt protective layer, tread rubber located between tread width direction outer end of Deb tread and belt protective layer tread width direction Thickness, Dbt Belt protection layer tread width direction outermost end and spiral belt layer folded part tread Tread rubber thickness, TG tread ground end, Tw tread ground width, Ws spiral belt layer tread width width, Wbp belt protective layer tread width width, Wtr spiral The tread width direction distance between the outermost end in the tread width direction of the belt layer and the inner end in the tread width direction of the spiral belt layer folded portion, and the inclination angle of the θ1, θ2 cord with respect to the tread circumferential direction

Claims (4)

A spiral belt layer formed by rubber-coating a plurality of cords arranged in parallel to each other and extending in the tread circumferential direction on the tread of the tire, and located on the outer side in the tire radial direction from the spiral belt layer and arranged in parallel to each other A pneumatic tire having a belt protective layer formed by rubber-covering a plurality of cords extending in the width direction, and a tread rubber positioned outward in the tire radial direction of the belt protective layer,
The tread rubber positioned between the outermost ends in the tread width direction of the belt protective layer as compared with the thickness Deb of the tread rubber positioned between the tread ground end and the outermost end in the tread width direction of the belt protective layer. of thickness Dbb is rather large,
The spiral belt layer has a spiral belt layer main body portion extending between both outermost ends in the tread width direction of the spiral belt layer, and at least one of both end portions of the spiral belt layer is inward in the tire radial direction or tire diameter. It consists of a spiral belt layer folded part folded back from the outside in the tread width direction toward the tire equator side,
The inner end of the spiral belt layer folded portion in the tread width direction is located on the inner side in the tread width direction of the outermost end in the tread width direction of the belt protective layer,
Compared to the thickness Deb of the rubber, the thickness Dbt size of the tread rubber located between the tread width direction inside end of the tread width direction outermost end of the belt protective layer and the spiral belt layer folded portion Ikoto Pneumatic tire characterized by   2. The pneumatic tire according to claim 1, wherein the rubber thickness Deb and the rubber thickness Dbb satisfy a relationship of 1.1 ≦ Dbb / Deb ≦ 1.4. 3. Characterized in that the tread width direction outermost end of the belt protective layer, a tread width direction between the tread width direction inside end of the spiral belt layer folded portion is 10 mm to 30 mm, according to claim 1 or 2 Pneumatic tires. It has an intersecting belt layer composed of two belt layers, which are located inward in the tire radial direction from the spiral belt layer and are rubber-coated with a plurality of cords arranged parallel to each other and extending inclined in the tread circumferential direction. The pneumatic tire according to any one of claims 1 to 3 , wherein:

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