JP2966752B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having improved grip performance on icy and snowy roads and improved straight running stability and turning performance.

[0002]

2. Description of the Related Art Studless tires are widely used to prevent road surfaces from being damaged by spike tires. In this type of tire, conventionally, in order to exert a grip force on an icy road, the number of sipes formed in the block is increased, and the frictional force is increased by digging a road surface by a siping edge or the like.

[0003]

However, in such a conventional tire, when the number of sipings is excessive, the rigidity of the block is insufficient, so that the block collapses and the frictional force is reduced. Performance is limited. In addition, when the block rigidity is insufficient as described above, the cornering power of the tire is reduced, and the steering stability during straight running and turning on a dry road surface is greatly impaired.

Therefore, in order to further improve the performance on ice and snow, it is necessary to make the siping function most effectively, and for this purpose, the present inventors have accumulated various studies. As a result, since the conventional siping a is formed substantially at right angles to the tread surface, as shown in FIG. 8, the block b is easily inclined and deformed in a direction away from the road surface due to the external force F received from the road surface during traveling. As a result, the contact pressure and the contact area are reduced. On the other hand, when the siping a is tilted in the direction facing the external force F, the block b is compressed in the direction of cutting into the road surface as shown in FIG. Deformation, which increases the block stiffness, increases the contact pressure and increases the contact area; and the tread surface is generally curved in a convex arc, so that the circumferential length of the tread differs between the center side and the shoulder side. In addition, it was found that the slip direction of the tread contact surface with the road surface, that is, the action direction of the external force F is different between the center side and the shoulder side.

[0005] Then, by forming sipes having different inclination directions on the center side and the shoulder side of the tread, and making each siping oppose an external force from a road surface, the contact pressure and the contact area can be greatly improved. It has been found that the coefficient of road friction can be most effectively increased for the tire as a whole.

That is, according to the present invention, the sipes of the projections arranged in the central tread area are inclined in the same direction as the rotation of the tire, and the sipes of the projections arranged in the shoulder tread area are defined as the rotation of the tire. Provides pneumatic tires that can exert the frictional force against the road surface due to siping most effectively, improve grip performance on ice and snowy roads, improve straight running stability, and cornering performance based on inclining in the reverse direction It is an object.

[0007]

In order to achieve the above object, a pneumatic tire according to the present invention comprises a vertical tread extending in a circumferential direction of the tire and a lateral groove extending in a direction crossing the vertical tread. By forming a plurality of ribs extending in the circumferential direction of the tire or a plurality of projecting strips formed of a row of blocks arranged in the circumferential direction of the tire, the tread contact surface is separated from the tire equator by 1 / (the width of the tread contact surface). 4 and a shoulder contact surface area on the outer side in the tire axial direction of the center contact surface area at a distance L, the central protrusion on the central contact surface area is located at the center contact surface area. A sipe that traverses the body in the tire axial direction and is inclined in the same direction as the tire rotation direction from the inside to the outside in the tire radial direction, and is provided in the shoulder contact surface area. Projecting strip of holder is equipped with sipes inclined in a direction opposite the protrusion strip of the shoulder across the tire axial direction and the inside of the tire radial direction and the tire rotational direction toward the outside.

[0008] Further, the siping of the central projecting strip is as follows.
The inclination angle θ1 with respect to the normal on the tread surface is 5 to 30 degrees,
Further, in the siping of the projecting strip of the shoulder, the inclination angle θ2 with respect to the normal to the tread surface is preferably 5 to 30 degrees.

[0009]

When the tires on the driving wheel side are braking and when the tires on the non-driving wheel side are braked and driven, as shown in FIG. An external force F directed in the traveling direction acts from the road surface. Therefore, by inclining the siping in the central ground contact area in the same direction as the tire rotation direction, the external force F and the siping oppose each other, increasing the block rigidity,
Increase the contact pressure and contact area, and increase the road surface friction force.

In the shoulder contact area, the circumferential length of the tread is smaller than that of the central contact area. Therefore, as shown in FIG. Acts in the opposite direction to the central tread area. Therefore, by inclining the siping in the shoulder contact area in the direction opposite to the tire rotation direction, the external force F and the siping oppose each other, and similarly, the road surface frictional force increases.

As described above, in the present application, the frictional force with the road surface due to siping is exerted most effectively, and the road surface frictional force is increased over the entire surface of the tread contact surface. The turning performance can be greatly improved. The effect of improving the road surface frictional force is similarly exerted on a wet road surface. Further, since the siping increases the rigidity of the block at the time of contact with the ground, the cornering power of the tire is increased, and it is also possible to contribute to the improvement of the steering stability on a dry road surface.

Note that the inclination angles θ1 and θ2 of the siping are
If the angle is less than 5 degrees, the above effect is insufficient. The effect is improved as the inclination angles θ1 and θ2 are increased. However, if the inclination angle is larger than 30 degrees, it is difficult to manufacture the tire, and when the tire is removed from the vulcanizing mold, the tire is easily cracked at the siping portion. .

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a pneumatic tire 1 (hereinafter referred to as tire 1).
2 shows a meridional section of a tire in a standard state in which is mounted on a standard rim and filled with standard internal pressure. Here, the standard rim is a standard rim in JATMA standard (Japan), TRA
The standard rim refers to a measurement rim in the standard (USA) and the ETRTO standard (Europe), and the standard internal pressure refers to an internal pressure 0.9 times the air pressure specified as the maximum air pressure in each of the above standards. Further, when a load of 0.9 times the maximum load specified in each standard is applied to the tire in the standard state, a width region in the tire axial direction where the tread surface comes into contact with the tire is defined as a tread contact surface S.

In the figure, a tire 1 has a pair of bead portions 3 through which a bead core 2 passes, a sidewall portion 4 extending outward from each bead portion 3 in the tire radial direction, and a tread portion 5 connecting the outer ends thereof. In this example, the tire is a passenger car tire, which is reinforced by a carcass 6 straddling between the bead portions 3 and the tough belt layer 7 wound around the bead portions 3 and imparts necessary tire rigidity. Is done.

The carcass 6 is formed from one or more carcass plies having carcass cords arranged at an angle of 70 to 90 degrees with respect to the tire equator C, in this example, one carcass ply. Both ends are folded back and locked around the bead core 2 through the wall portion 4. Carcass cords include steel cord, nylon,
Organic fiber cords such as rayon and polyester are employed.

The belt layer 7 is composed of a plurality of belt cords in which belt cords are arranged at an angle of 0 to 30 degrees with respect to the tire equator C, in this example, two belt plies, and the cords cross each other between the plies. In different directions. As the belt cord, similarly to the carcass cord, a metal fiber cord such as steel and an organic fiber cord such as nylon, polyester and rayon are used.
Has a hammer effect over substantially the entire width and enhances rigidity.

The surface (tread surface) of the tread portion 5 is provided with a vertical main groove G extending in the circumferential direction of the tire and a horizontal groove Y extending in a direction crossing the vertical main groove G. On S, a plurality of ribs or ribs extending in the tire circumferential direction or a plurality of projecting strips 10 formed of a block row in which the blocks are arranged in the tire circumferential direction are formed. Also, the tread contact surface S
Distance L from tire equator C to 1/4 of tread contact surface width W
Is divided into a central tread area S1 and a shoulder tread area S2 on the outer side in the tire axial direction, a siping 11 is provided on a central protruding strip 10A arranged in the central tread area S1. , The shoulder contact area S2
12 on the shoulder projections 10B
Is provided.

In the tread profile of the tire in the standard state, at least the center contact surface area S1 is formed of a single arc having a center on the tire equatorial plane and a radius of curvature R of 200 to 2000 mm. The outer shoulder contact surface area S2 is formed by a single or compound arc having a radius of curvature equal to or less than the radius of curvature R. In this example, the tread contact surface S is a central contact surface area S1.
And a single circular arc having the same radius of curvature of the shoulder contact surface area S2.

In this embodiment, as shown in FIG. 2, the vertical main groove G includes a vertical main groove Gi extending on the tire equator C and an external vertical main groove disposed outside the tire axial direction. The horizontal groove Y includes a horizontal groove Ym extending between the vertical main grooves Gi and Go, and an external horizontal groove Yo connecting the vertical main groove Go and the tread grounding edge E. Therefore, the vertical main grooves Gi, G
Between o, a block row in which the middle blocks Bm are arranged in the tire circumferential direction is formed, and this block row constitutes the central projection strip body 10A by being completely located in the central ground contact surface area S1. . Further, between the vertical main groove Go and the tread contact edge E, a block row in which the outer blocks Bo are arranged in the tire circumferential direction is formed, and this block row is completely located in the shoulder contact surface area S2. This constitutes the shoulder strip 10B of the shoulder. The vertical main groove G
Groove width Wg is in the range of 3 to 8% of tread tread width W,
For example, it is set to about 5 to 12 mm, and the groove depth Hg is set to a range of 5 to 10% of the tread contact surface width W, for example, about 8 to 15 mm. The width W of the lateral groove Y
It is preferable to set y and the groove depth Hy to be equal to or slightly smaller than the groove width Wg and the groove depth Hg of the vertical main groove G.

The sipes 11 arranged on the central protruding strip 10A have a linear shape crossing the protruding strip 10A in the axial direction of the tire, and have a pitch equal to that of other sipes adjacent in the tire circumferential direction. They are arranged parallel to each other at an incorrect pitch. The siping 11 is, as shown in FIG.
The tire is inclined in the same direction as the tire rotation direction K from the inner side to the outer side in the tire radial direction, and the inclination angle θ1 with respect to the normal line n on the tread surface is in the range of 5 to 30 degrees.

Similarly, the sipes 12 arranged on the projections 10B of the shoulder have a linear shape crossing the projections 10B in the tire axial direction, and are similar to other sipes adjacent in the tire circumferential direction. They are arranged parallel to each other at a pitch or an incorrect pitch. Further, as shown in FIG. 4, the siping 12 is inclined in a direction opposite to the tire rotation direction K from the inside to the outside in the tire radial direction, and the inclination angle θ2 with respect to the normal line n on the tread surface is 5 to 30 degrees. Of the range.

Siping 11 in the central ground contact area S1
By tilting in the same direction as the tire rotation direction,
When the tire on the driving wheel side brakes and the tire on the non-driving wheel side brakes and drives, as shown in FIG. 5, by opposing the external force F from the road surface, the projecting strip 10A is moved toward the road surface side. It compresses and deforms in the biting direction, increases the pattern rigidity, increases the contact pressure and contact area, and increases the road surface frictional force.

In the shoulder contact area S2, the circumferential direction of the tread is smaller than that of the central contact area S1, so that the direction in which the external force F acts is opposite to that of the central contact area S1. Therefore, as shown in FIG. 6, by tilting the siping 12 in the direction opposite to the tire rotation direction, the siping 12 opposes the external force F and similarly increases the road surface frictional force.

The effect of improving the road surface frictional force by the sipes 11 and 12 can be most effectively exerted when the radius of curvature R of the tread is in the range of 200 to 2000 mm, more preferably 600 mm or less.

The effect of improving the road surface frictional force increases as the inclination angles θ1 and θ2 increase. However, if the inclination angle is larger than 30 degrees, it is difficult to manufacture the tire.
If the degree is smaller than the above, the above effect is insufficient.

Each siping 11, 12 preferably has a width in the axial direction of the tire on the tread surface of 0.5 to 1.5 mm. It causes excessive decrease in rigidity such as separation,
When the thickness is less than 0.5 mm, the grip property on a snowy road surface is reduced, and the durability of the vulcanization forming mold is impaired.

The depth Ha, H of each siping 11, 12
b is preferably 0.5 to 1.0 times the groove depth Hg of the vertical main groove G, and when less than 0.5 Hg, the effect of improving the road surface frictional force is reduced. In addition, when it is larger than 1.0 Hg, although there is no adverse effect on the road surface frictional force improving effect, it is necessary to increase the rubber gauge of the entire tread portion 5 in order to secure the rubber thickness under the siping, and the weight of the tire increases. Invite. Therefore, it is more preferable that the siping depths Ha and Hb be equal to or less than the groove depth Hg and a difference between the groove depths Hg be within 1 mm.

The effect of improving the road surface frictional force is also exerted on a wet road surface.
The tire 12 increases the rigidity of the block when it touches the ground, so that the cornering power of the tire is increased and it is possible to contribute to the improvement of the steering stability on a dry road surface.

The central projection strip 10A and the shoulder projection strip 10B are the projection strips 10 whose entire surfaces are located in the center contact surface area S1 and the shoulder contact surface area S2. In other words, FIG. 9 shows another embodiment of the present application in which the surface of the projection strip 10 extends over both the center contact surface area S1 and the shoulder contact surface area S2.

As shown in FIG. 9, the tread contact surface S has a central protruding strip 10 disposed in the central contact surface area S1.
A, a shoulder strip 10B disposed in the shoulder contact surface area S2 and an intermediate protrusion 10C whose surface extends over both the central contact surface area S1 and the shoulder contact surface area S2 are formed. The projecting strips 10A, 10B, 10C are:
In addition to the formation of the block rows as in this example, a rib body excluding the lateral groove Y may be formed, or the block rows and the rib bodies may be appropriately mixed to form a tread pattern. A siping 11 is provided on the central protrusion 10A.
However, the sipe 12B is provided on the shoulder projection 10B.
Are formed respectively.

The siping 13 formed on the intermediate projecting strip 10C may be formed at an inclination angle of 0 ° parallel to the normal line n. When it is located in the region S1, it is inclined in the same direction as the tire rotation direction K as in the siping 11, and when its centroid is located in the shoulder contact surface region S2, it is opposite to the tire rotation direction K as in the sipe 12. It is preferable to tilt in the direction. Note that the centroid is the centroid of the developed view in the tire circumferential direction on the surface of the intermediate projection strip 10C, and coincides with the position of the center of gravity when the mass is uniformly distributed on the developed view.

(Specific Example) Tire size 175/80 having the tire structure of FIG. 1 and forming the tread pattern of FIG.
R1 88Q tires were prototyped based on the specifications in Table 1, and each test tire was tested on a rim (14x5J) and internal pressure (front wheel: 2.0 ksc, rear wheel: 1.9 ksc).
Mounted on the four wheels of an F car (1800 cc) on a snowy road (snow temperature:
(-3 ° C., air temperature: -8 ° C.), the vehicle was run, and the straight running stability performance and the turning performance at that time were evaluated by a 10-point scale based on the feeling of the driver. The larger the index, the better.

[0033]

[Table 1]

[0034]

Since the pneumatic tire of the present invention is constructed as described above, it can exert the most effective frictional force against the road surface due to siping, enhance grip performance on ice and snowy roads, and maintain straight running stability. , Turning performance can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire showing one embodiment of the present invention.

FIG. 2 is a plan view showing an example of the tread pattern.

FIG. 3 is a cross-sectional view in the tire circumferential direction showing a siping of a central protruding strip.

FIG. 4 is a cross-sectional view in the tire circumferential direction showing siping of a projection strip of a shoulder.

FIG. 5 is a cross-sectional view showing a grounded state of a central protruding strip.

FIG. 6 is a cross-sectional view showing a grounded state of a projection strip of a shoulder.

FIG. 7 is an operation diagram illustrating an operation by siping of the present invention.

FIG. 8 is an operation diagram illustrating an operation by conventional siping.

FIG. 9 is a plan view of a tread pattern showing another embodiment of the present invention.

FIG. 10 is a plan view showing a tread pattern of a comparative example product used in a specific example.

[Explanation of symbols]

 10, 10A, 10B, 10C Protrusions 11, 12, 13 Siping S Tread tread area S1 Central tread area S2 Shoulder tread area C Tire equator G, Gi, Go Vertical main groove Y, Yi, Yo Horizontal groove

Claims (2)

(57) [Claims] A tread contact surface is defined by a vertical main groove extending in a tire circumferential direction and a horizontal groove extending in a direction crossing the vertical main groove, so that a rib or a block extending in the tire circumferential direction is formed in the tire circumferential direction. While forming a plurality of projecting strips composed of a row of blocks arranged, the tread contact surface is connected to a central contact surface area separated from the equator of the tire by a distance L of 1/4 of the width of the tread contact surface, and to a shoulder contact outside the tire axial direction. When virtually divided into the ground area, the central protruding strip disposed in the center tread area crosses the central protruding strip in the tire axial direction and rotates the tire from the inner side to the outer side in the tire radial direction. A siping inclined in the same direction as the direction is provided, and the shoulder ridges arranged in the shoulder contact surface area cross the shoulder ridges in the tire axial direction. A pneumatic tire is a tire rotational direction from the inside to the outside in the tire radial direction, characterized in that it comprises the sipes inclined in opposite directions. 2. The sipe of the central projection strip has an inclination angle θ1 with respect to the normal on the tread surface of 5 to 30 degrees, and the sipe of the shoulder projection strip has an inclination with respect to the normal on the tread surface. The pneumatic tire according to claim 1, wherein the angle? 2 is set to 5 to 30 degrees.