JPH08230416A - Pneumatic tire - Google Patents

Abstract

PURPOSE: To increase road surface frictional force by providing a siping, which slants in the reverse direction to the tire rotating direction, in a projection bar body on a shoulder when a tread surface is sectioned imaginarily into a center tread surface area within the predetermined distance in the tread surface width direction of a tire equator and a shoulder tread surface area. CONSTITUTION: On the surface of a tread part, 5, a longitudinal main groove G extending in the tire circumference direction and a lateral groove Y extending in the direction crossing the longitudinal groove G are arranged. On a tread surface S, a plurality of projection bar bodies 10 consisting of block rows, in which ribs or blocks extending in the tire circumference direction are arranged in the tire circumference direction, are formed. When the tread surface S is divided imaginarily into a center tread surface area S1 within a distance L, which is a quarter of the tread surface width W, of a tire equator C and a shoulder tread surface area S2 on the outside in the tire axis direction, a siping 11 is arranged in the center projection bar body 10A arranged in the center tread surface area S1, while a siping 12 is arranged in the projection bar body 10B arranged in the shoulder tread surface area S2.

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 ice 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 damage to the road surface due to spiked tires. In this type of tire, conventionally, in order to exert a gripping force on an icy and snowy road, the number of sipings formed on the block is increased to dig up the road surface by a siping edge or the like to increase the frictional force.

[0003]

However, in such a conventional tire, the block rigidity is insufficient due to an excessive number of sipings, which causes the block to collapse, which in turn causes a reduction in frictional force. Upper performance is limited. Moreover, if the block rigidity becomes insufficient in this way, the cornering power of the tire is reduced, and the steering stability performance during straight running and turning on a dry road surface is greatly impaired.

[0004] Therefore, in order to further improve the performance on ice and snow, it is necessary for the siping to function most effectively, and therefore, the present inventor has conducted 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, an external force F received from the road surface during traveling causes the block b to be easily inclined and deformed in a direction away from the road surface, As a result, the ground contact pressure and the ground contact area are reduced; on the other hand, when the siping a is tilted in a direction facing the external force F, the block b is compressed in a direction in which the block b bites into the road surface side, as shown in FIG. Deformation, which increases the rigidity of the block, increases the contact pressure and increases the contact area; and the tread surface is generally curved in the shape of a convex arc, which causes the tread circumference to be different between the center side and the shoulder side. In addition, the slip direction of the tread contact surface with the road surface, that is, the acting direction of the external force F is different between the center side and the shoulder side.

By forming sipings having different inclination directions on the center side and the shoulder side of the tread, and making the respective sipes face the external force from the road surface, the ground pressure and the ground area can be greatly improved. It has been found that the road surface friction coefficient can be most effectively increased in the tire as a whole.

That is, according to the present invention, the siping of the projecting body disposed in the central ground contact area is inclined in the same direction as the tire rotation, and the siping of the projecting body disposed in the shoulder ground contact area is referred to as the tire rotation. Based on tilting in the opposite direction, the pneumatic tire that can maximize the frictional force with the road surface by siping, enhance the grip performance on ice and snow roads, improve straight running stability and turning performance It is an object.

[0007]

In order to achieve the above object, the pneumatic tire of the present invention has a tread contact surface formed by a vertical main groove extending in the tire circumferential direction and a horizontal groove extending in a direction transverse to the vertical main groove. By partitioning the ribs extending in the tire circumferential direction, or a plurality of protrusions formed of a row of blocks in which blocks are arranged in the tire circumferential direction, the tread contact surface is divided from the tire equator to 1 / th of the tread contact surface width. 4 is virtually divided into a central ground contact surface area separated by a distance L of 4 and a shoulder ground contact surface area outside of the tire axial direction, the central projection strip disposed in the central ground contact surface area is the central projection strip. The body is provided with a siping that traverses the body in the axial direction of the tire and inclines in the same direction as the tire rotation direction from the inner side to the outer side in the tire radial direction, and is arranged in the shoulder ground contact 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.

Also, the siping of the central protrusion is
The inclination angle θ1 with respect to the normal line on the tread surface is 5 to 30 degrees,
Moreover, it is preferable that the sipe of the ridge of the shoulder has an inclination angle θ2 of 5 to 30 degrees with respect to the normal to the tread surface.

[0009]

When the tire on the driving wheel side is braking and the tire on the non-driving wheel side is braking / driving, as shown in FIG. 5, the central tread area of the tread is opposite to the tire rotating direction. An external force F directed in the traveling direction is applied from the road surface. Therefore, by tilting 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 and the block rigidity is increased,
The ground contact pressure and the ground contact area are increased, and the road surface friction force is increased.

Further, in the shoulder contact surface area, the tread circumference is smaller than that in the central contact surface area. Therefore, as shown in FIG. 6, the slip direction with respect to the road surface, that is, the direction of the external force F. Acts in the opposite direction to the central ground plane area. Therefore, by tilting the siping in the shoulder contact surface area in the direction opposite to the tire rotation direction, the external force F and the siping oppose each other, and the road surface friction force is similarly increased.

As described above, according to the present invention, the frictional force with the road surface due to the siping is most effectively exerted, and the road surface frictional force is increased over the entire tread contact surface. The turning performance can be greatly improved. In addition, such an effect of improving the road surface friction force is also exhibited on a wet road surface. Further, since the above-mentioned siping enhances the block rigidity at the time of contact with the ground, the cornering power of the tire is increased and it is possible to contribute to the improvement of steering stability on a dry road surface.

The inclination angles θ1 and θ2 of the siping are
If it is less than 5 degrees, the above effect is insufficient. Further, the above effect is improved as the tilt angles θ1 and θ2 increase, but if the tilt angle is more than 30 degrees, it is difficult to manufacture the tire, and when the tire is taken out from the vulcanization mold, crack damage is likely to occur in the tire at the siping portion. .

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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)
3 shows a meridional section of a tire in a standard state in which the tire is assembled on a standard rim and filled with a standard internal pressure. Here, the standard rim refers to the standard rim in JATMA standard (Japan), TRA
Standard (US) and ETRTO standard (Europe) measurement rims, and standard internal pressure means an internal pressure 0.9 times the air pressure specified as the maximum air pressure in each of the standards. Further, a width region in the tire axial direction where the tread surface contacts the ground when a load of 0.9 times the maximum load defined in each standard is applied to the tire in the standard state is defined as a tread contact surface S.

In the figure, a tire 1 includes 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 radial direction of the tire, and a tread portion 5 connecting the outer ends thereof. In this example, the tire is for a passenger car and is reinforced by a carcass 6 straddling between the bead portions 3 and 3, a tough belt layer 7 wound around the carcass 6 and the like, and is provided with necessary tire rigidity. To be done.

The carcass 6 is formed by one or more carcass plies in which carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire equator C, and 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 cords, nylon,
Organic fiber cords such as rayon and polyester are used.

The belt layer 7 is composed of a plurality of belt plies 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 plies, and the cords cross each other. And place them in different directions. Similar to the carcass cord, a metal fiber cord such as steel and an organic fiber cord such as nylon, polyester or rayon are used as the belt cord.
Has a hoop effect over almost the entire width to reinforce and increase rigidity.

The surface (tread surface) of the tread portion 5 is provided with a longitudinal main groove G extending in the tire circumferential direction and a lateral groove Y extending in a direction traversing the longitudinal main groove G. In S, a plurality of ribs 10 extending in the tire circumferential direction or a plurality of protruding strips 10 each including a block row in which blocks are arranged in the tire circumferential direction are formed. In addition, the tread contact surface S,
Distance L from the tire equator C to 1/4 of the tread contact surface width W
When the virtual ground is divided into a central ground contact surface area S1 and a shoulder ground contact surface area S2 outside the tire axial direction, the siping 11 is provided on the central protruding strip 10A arranged in the central ground contact surface area S1. , The shoulder contact area S2
On the shoulder protrusion 10B arranged in the
To provide.

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

In this embodiment, as shown in FIG. 2, the vertical main groove G includes an internal vertical main groove Gi extending on the tire equator C and an external vertical main groove arranged outside the tire axial direction. The lateral groove Y includes Go and Go, and the lateral groove Y includes a lateral groove Ym that connects the vertical main grooves Gi and Go, and an external lateral groove Yo that connects the vertical main groove Go and the tread ground edge E. Therefore, the vertical main grooves Gi, G
A block row in which the inner blocks Bm are arranged in the tire circumferential direction is formed between o, and the block row configures the central protruding strip 10A by being completely located in the central ground contact surface area S1. . Further, between the vertical main groove Go and the tread ground contact edge E, a block row in which outer blocks Bo are arranged in the tire circumferential direction is formed, and this block row is completely located within the shoulder ground contact surface area S2. Thus, the shoulder protrusion 10B is formed. The vertical main groove G
Groove width Wg of 3 to 8% of the tread ground contact surface width W,
For example, the groove depth Hg 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 ground contact surface width W, for example, about 8 to 15 mm. The width W of the lateral groove Y
y and the groove depth Hy are preferably set to be equal to or slightly smaller than the groove width Wg and the groove depth Hg of the vertical main groove G.

Further, the siping 11 arranged on the central protruding strip 10A has a straight line shape that traverses the protruding strip 10A in the tire axial direction, and has the same pitch as other sipings adjacent to the tire circumferential direction or Arrange in parallel with each other at an incorrect pitch. The siping 11 is, as shown in FIG.
The tire is inclined from the inner side to the outer side in the tire radial direction in the same direction as the tire rotation direction K, 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 siping 12 arranged on the shoulder protruding body 10B has a straight line shape that traverses the protruding protruding body 10B in the tire axial direction, and is the same as other sipings adjacent in the tire circumferential direction. They are arranged in parallel with each other with a pitch or an incorrect pitch. As shown in FIG. 4, the siping 12 inclines in the tire radial direction from the inner side to the outer side in the direction opposite to the tire rotation direction K, and has an inclination angle θ2 of 5 to 30 degrees with respect to the normal line n on the tread surface. And the range.

Siping 11 of 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 when the tire on the non-driving wheel side brakes / drives, as shown in FIG. 5, by opposing the external force F from the road surface, the projection strip 10A is moved to the road surface side. By compressing and deforming in the direction of biting, the pattern rigidity is increased, the ground contact pressure and the ground contact area are increased, and the road surface friction force is increased.

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

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

Further, the road surface frictional force improving effect is improved as the inclination angles θ1 and θ2 increase, but if the inclination angles θ1 and θ2 are larger than 30 degrees, it is difficult to manufacture a tire, and conversely, the inclination angles θ1 and θ2 are 5 degrees.
If the degree is smaller than the above, the above effect becomes insufficient.

The width of each of the sipings 11 and 12 in the axial direction of the tire on the tread surface is preferably 0.5 to 1.5 mm. Inducing excessive reduction in rigidity such as separation,
On the other hand, when it is less than 0.5 mm, not only the grip property on a snowy road surface is reduced, but also the durability of the vulcanization mold is impaired.

Further, the depths Ha and H of the respective sipings 11 and 12 are
b is preferably 0.5 to 1.0 times the groove depth Hg of the vertical main groove G, and when it is less than 0.5 Hg, the effect of improving the road surface friction force decreases. When it is larger than 1.0 Hg, the road surface frictional force improving effect is not adversely affected, but it is necessary to increase the rubber gauge of the entire tread portion 5 in order to secure the rubber thickness under siping, which increases the weight of the tire. Invite. Therefore, it is more preferable that the siping depths Ha and Hb be less than or equal to the groove depth Hg and less than 1 mm from the groove depth Hg.

Further, such an effect of improving the road surface frictional force is exhibited even on a wet road surface, and the siping 11,
Since No. 12 increases the block rigidity at the time of contact with the ground, the cornering power of the tire is increased, which can contribute to the improvement of steering stability on dry road surfaces.

The central ridge 10A and the shoulder ridge 10B are those of which the entire surface is located within the central ground contact area S1 and the shoulder ground contact area S2. FIG. 9 shows another embodiment of the present application in which the surface of the protrusion 10 extends over both the central ground contact area S1 and the shoulder ground contact area S2.

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

The siping 13 formed on the intermediate ridge 10C may be formed at an inclination angle of 0 degree parallel to the normal line n, but the centroid of the surface of the intermediate ridge 10C is the central ground plane. When it is located in the area S1, it is inclined in the same direction as the tire rotation direction K like the siping 11, and when it is located in the shoulder ground contact surface area S2, it is opposite to the tire rotation direction K like the siping 12. It is preferable to incline in the direction. The centroid is a centroid of a circumferential development view of the tire on the surface of the intermediate ridge 10C, and coincides with the center of gravity position when the mass is uniformly distributed on the development view.

(Specific Example) Tire size 175/80 having the tire structure of FIG. 1 and the tread pattern of FIG.
R14 88Q tires were prototyped according to the specifications in Table 1, and each sample tire was tested with rim (14x5J) and internal pressure (front wheel: 2.0ksc, rear wheel: 1.9ksc).
Installed on the four wheels of the F car (1800 cc), the snowy road (snow temperature:
The actual vehicle was run at -3 ° C, temperature: -8 ° C), and the straight running stability and turning performance at that time were evaluated by the driver's feeling using a 10-point scale. The larger the index, the better.

[0033]

[Table 1]

[0034]

Since the pneumatic tire of the present invention is constructed as described above, the frictional force with the road surface due to siping can be most effectively exhibited, the grip performance on the ice and snowy road is enhanced, and the straight running stability performance is improved. The turning performance can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire showing an 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 siping of a central protruding strip.

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

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

FIG. 6 is a cross-sectional view showing a grounded state of a ridge 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 product used in a specific example.

[Explanation of symbols]

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

Claims (2)

[Claims] 1. A rib or block extending in the tire circumferential direction is defined in the tire circumferential direction by partitioning a tread contact surface with a vertical main groove extending in the tire circumferential direction and a lateral groove extending in a direction crossing the vertical main groove. While forming a plurality of ridges composed of lined block rows, the tread contact surface is separated from the tire equator by a central contact area separated from the tire equator by a distance L of 1/4 of the tread contact width and a shoulder contact on the outer side in the tire axial direction. When it is virtually divided into the ground area, the central protruding strip disposed in the central ground contact surface 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. The shoulder ridges arranged in the shoulder ground contact surface area have a sipe inclined in the same direction as the direction, and the shoulder ridges 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 ridge has an inclination angle θ1 of 5 to 30 degrees with respect to the normal to the tread surface, and the sipe of the shoulder ridge has an inclination to the normal to the tread surface. The pneumatic tire according to claim 1, wherein the angle θ2 is 5 to 30 degrees.