JP2923797B2 - Pneumatic radial tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic radial tire having improved cornering performance on icy roads while taking into account, to some extent, dry performance after a middle wear period.

[Conventional technology]

Conventional studless tires have been aimed at improving performance mainly for linear movement, such as starting performance, acceleration performance and braking performance on icy roads.

However, in recent years, some consideration has been given to dry performance and abnormal wear, which allow tires to run on ice and snow roads, and to continue running on road surfaces after spring, when ice and snow have melted in the middle wear period. There is a need to improve cornering performance on ice and snow roads.

[Problems to be solved by the invention]

The present invention has been made in view of such demands, and aims to prevent dry performance after middle wear, especially abnormal wear after middle wear, and to reduce performance such as starting performance, acceleration performance and braking performance on icy and snowy roads. Another object of the present invention is to provide a pneumatic radial tire with improved cornering performance on icy and snowy roads.

[Means for solving the problem]

That is, the pneumatic radial tire of the present invention has a larger number of blocks by providing a plurality of main grooves extending in the tire circumferential direction on the tread surface and providing transverse grooves extending from the center portion to the shoulder portion so as to intersect with the main grooves. To form
And, in the pneumatic radial tire in which a plurality of kerfs in the tire circumferential direction are arranged in the shoulder block of the block, the density of the kerf in the tire width direction is set to a shoulder portion side half width region from the center portion side half width region density ρi. urban density [rho ₀ large, and together with the tilting angle α to the shoulder portion side the kerf for the profile normal, and characterized in that shallow part of calf high shoulder portion side half width area of calf density Is what you do.

Generally, when the steering wheel is operated to change the direction of travel of a vehicle that is traveling straight, the rotating surface of the tire will have a certain angle with respect to the direction of travel of the vehicle, but the vehicle will continue to travel straight due to inertia. Therefore, a deviation occurs between the rotation surface of the tire and the traveling direction of the vehicle.

When this happens, the wheels are in a state of being driven sideways, so that the tires undergo lateral deformation as a whole. Then, the center line of the tire and the center of the tread contact surface deviate from each other, so that the contact pressure on the shoulder portion side of the tire increases and the contact pressure on the center portion side decreases.

The present invention has specified the density and the inclination angle of the kerf disposed on the shoulder block so as to exhibit the edge force of the kerf most efficiently at the time of cornering from the knowledge of such a variation in the contact pressure of the tire. Things.

In the present invention, it is necessary to set the density [rho ₀ of the shoulder portion side half width area than the density ρi of the center portion side half width area the density of the tire widthwise direction of the kerf to atmospheric. That is, by making the density ρ ₀ of the kerf in the shoulder-side half-width region larger than the density ρi of the kerf in the center-portion half-width region, the edge of the kerf in the shoulder-portion half-width region becomes the edge of the kerf in the center-portion half-width region. More than in comparison. Therefore, when the contact pressure on the shoulder side increases during cornering, the number of edges that bite into the road surface, that is, the icy and snowy surface, increases, and the cornering performance is improved.

Further, in the present invention, it is necessary to incline the kerf toward the shoulder side by an angle α with respect to the profile normal. That is, the kerf is inclined toward the shoulder portion side by inclining the kerf toward the shoulder portion side with respect to the profile normal line. Therefore, when the contact pressure on the shoulder side increases during cornering, the edge of the kerf stands and the cornering performance is improved.

Here, the profile normal refers to a straight line perpendicular to a tangent to the tread surface.

Further, in the present invention, it is necessary to make a part of the kerf in the shoulder part side half width region having a high kerf density shallow.
That is, if a part of the kerf in the half width region on the shoulder side having a high kerf density is made shallow, the kerfs in the shallow grooves disappear by the middle period of wear, so only the deep kerfs of the grooves arranged at equal intervals remain. Has a substantially uniform calf density, so that abnormal wear of the tire after the middle stage of wear can be prevented.

Hereinafter, the pneumatic radial tire of the present invention will be described with reference to the drawings.

FIG. 1 is an exploded view of a tread pattern of a pneumatic radial tire according to the present invention.
Is provided with a first main groove 2 having a zigzag shape extending in the tire circumferential direction. Also, one zigzag second main groove 3 is provided on each side. Further, the main grooves 2 and 3 are crossed by lateral grooves 4 and 5 extending from the center portion C toward the shoulder portion S toward the shoulder portion S.
6,7 are formed. A large number of kerfs 8 extending in the tire circumferential direction are provided in the block 7 on the shoulder portion S side of the blocks 6 and 7.

As shown in FIG. 2, the density of the kerf 8 in the tire width direction is such that the density ρ ₀ of the kerf in the half width region o on the shoulder portion S side is the density ρi of the kerf in the half width region i on the center portion C side.
Is getting bigger.

Further, as shown in FIG. 3, the calf 8 is inclined toward the shoulder S by an inclination angle α with respect to a profile normal 10 perpendicular to a tangent 9 contacting the tread surface 1. In order to exhibit cornering performance on ice and snowy roads, it is preferable that the inclination angle α be in the range of 15 to 25 °.

Now, when a tire having the above-described tread pattern is mounted on a vehicle and a steering operation is performed, the block 7 on the shoulder portion S receives a force in the tire lateral direction as indicated by an arrow as shown in FIG. . Then, the edge 7A of the block 7 and the edge 8A of the calf 8 in the shoulder-side half-width region bite into the ice and snow surface 11, and a cornering force of the tire is generated. At this time, because there is a large density [rho ₀ kerf of high ground contact pressure shoulder portion side half width area, higher corner rig force is generated, cornering performance is significantly improved.

On the other hand, the tire of the present invention is designed to prevent abnormal wear of the tire after the middle stage of wear. That is, the tire, shallow part of the calf 8 provided in the region o the large shoulder portion side of the kerf density, sets the depth d ₂ to approximately one-half of the maximum groove depth d ₁ ing. The deep groove portion of the kerf 8 is oriented in the direction of the profile normal 10.

When the medium wear period is reached, as shown in FIG. 5, the shallow kerf 8 disappears due to abrasion, and only the deep kerf 8 remains at regular intervals. Can be.

The aforementioned calf 8 may be formed in a zigzag shape as shown in FIG. Further, as shown in FIG. 7, the block may not reach the end of the block 7. Further, as shown in FIG.
May be interrupted on the way.

〔Example〕

Table 1 shows the results of the evaluation of the steering stability on snow and the circular turning performance on ice in the actual vehicle for the comparative tires A, B, and C, in which the specifications of the tires were set as follows, and the tire of the present invention. That is, the specification of the tire (a) Comparative tire A As shown in FIG. 9, the density in the tire width direction of the kerf 8 provided in the block 7 on the shoulder portion side is changed to the density ρ ₀ of the kerf in the half width region on the shoulder portion side. And the density ρi of the kerf in the center-side half-width region were made substantially equal, and the inclination angle α of the kerf was set to 0 °.

(B) Comparative tire B As shown in FIG. 10, the density in the tire width direction of the kerf 8 provided in the block 7 on the shoulder portion side is calculated from the density ρi of the kerf in the center portion side half width region on the shoulder portion side. calf density [rho ₀ large cities, and the inclination angle α of the kerf was set to 0 °.

(C) Comparative tire C As shown in FIG. 9, the density in the tire width direction of the kerf 8 provided in the block 7 on the shoulder side is determined by the density ρ ₀ of the kerf in the half width area on the shoulder side and the half width on the center side. The kerf density ρi in the region was made substantially equal, and the kerf inclination angle α was set to 20 °.

(D) Tire of the present invention As shown in FIG. 10, the density in the tire width direction of the kerf 8 provided in the block 7 on the shoulder portion side is calculated from the density ρi of the kerf in the sensor portion side half width region on the shoulder portion side half width region. , The kerf density ρ ₀ is large, and the kerf inclination angle α is
Set to 20 ゜.

The evaluation of the above-mentioned steering stability performance on snow and circular turning performance on ice were performed as follows. That is, the evaluation tires are mounted on all wheels of the vehicle on which the steering stability is evaluated on snow, and the evaluation points of the steering performance by the driver's fouling on the snowy road are indicated by an index. The larger the index, the better the steering stability performance.

Circular turning performance on ice Evaluate tires are mounted on all wheels of the evaluation vehicle, enter the circular turning circuit on ice with a radius of 35 m at an initial speed of 10 km / h, accelerate, and increase the section time at the maximum speed that can maintain the radius of 35 m. Display as an exponent. The section time is shorter as the index is larger. That is, it indicates that the circular turning performance on ice is excellent.

The tire size is 215R15, rim size is 15 × 6J
J, the air pressure was 2.0 kgf / cm ² , and the evaluation car was Hilux Surf.

As a result, as shown in Table 1 above, the tire of the present invention has improved circular turning performance on ice without lowering steering stability on snow compared to comparative tires A, B and C. Do you get it.

〔The invention's effect〕

As described above, the present invention relates to a shoulder portion formed by providing a plurality of main grooves extending in a tire circumferential direction on a tread surface and a transverse groove extending from a center portion to a shoulder portion crossing the main groove. In a pneumatic radial tire in which a plurality of tire circumferential kerfs are arranged on a block,
Angle α is inclined to the shoulder portion side of the large cities, and the profile normal the kerf density [rho ₀ of the shoulder portion side half width area than the density ρi of the center portion side half width area the density of the tire width direction of the calf At the same time, part of the calf in the shoulder side half width area with high calf density is made shallow, so that abnormal wear after the middle wear is prevented, and performance such as starting performance, acceleration performance, braking performance etc. on ice and snow roads is not reduced. Cornering performance on icy and snowy roads can now be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a development view of a tread pattern of a pneumatic radial tire according to the present invention, FIG. 2 is a plan view of a shoulder block, and FIG. 3 is a cross-sectional view taken along the line III-III of FIG. Fig. 4 is a cross-sectional view showing an edge effect at the time of cornering on an icy road, Fig. 5 is a cross-sectional view of a block after the middle stage of wear, and Figs. 6 to 8 are pneumatic radial tires according to the present invention. 9 and 10 are plan views showing the tread pattern of the embodiment. 1 ... tread surface, 2,3 ... main groove, 4,5 ... lateral groove, 6,7 ...
... block, 8 ... calf, C ... center, S ...
Shoulder part.

Claims (1)

(57) [Claims] 1. A plurality of blocks are formed by providing a plurality of main grooves extending in a tire circumferential direction on a tread surface and providing transverse grooves extending from a center portion to a shoulder portion so as to intersect with the main grooves. In a pneumatic radial tire in which a plurality of kerfs in the tire circumferential direction are arranged on the shoulder block of the block, the density of the kerf in the tire width direction is set to the density of the shoulder portion half width region from the density ρi of the center portion side half width region. the [rho ₀ large cities and with tilting angle α to the shoulder portion side the kerf for the profile normal, shallow pneumatic radial tire for a portion of the calf of the high shoulder portion side half width area of calf density.