JPH06171319A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve traveling performance on both of a snowy road and an icy road in a well-balanced state. CONSTITUTION:A block pattern is formed on a tread part by utilizing circumference directional longitudinal grooves G1, G2 including a pair of main grooves GO, which extends in the tire circumferential direction and divides the tread part 5 into a crown part, TC on the tire equatorial side and a shoulder part TS on the outside of the crown part, TC. In regular inner pressure condition, a tread width TW is set to be 0.7-0.8 times of a tire cross section width W, a crown width TWC in the crown part, PC is set to be 0.4-0.6 times of the tread width TW, a radius of curvature TR1 of the crown part TC is set to be 2.7-3.1 times of the tread width TW and a radius of curvature TR2 of the shoulder part TS is set to be 2.2-2.6 times of the tread width TW. In a tread face of the tread part, the ratio of the total area of the blocks in the crown part TC to the total area A of the tread face is set to be 0.3-0.45, and the ratio of the total area of the blocks in the shoulder part TS to the total area A of the tread face is set to be 0.2-0.3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving snow running performance and ice running performance in a well-balanced manner.

[0002]

2. Description of the Related Art In recent years, so-called studless tires have been widely used as tires that can run on ice and snow roads.

In general, this type has a block pattern with a small land area ratio formed on the tread surface, and as shown in FIG. 4, the shearing force is obtained from the snow pillars that are set in the groove to improve the snow performance. ing. On the other hand, with respect to the performance on ice, siping in the tire axial direction is formed on each block while the tread portion is formed of a soft rubber material, and an ice friction scratching effect due to the adhesive frictional force with the ice road surface and the siping edge (Fig. 5). (Shown in each) is carried out.

[0004]

However, while the land area ratio can be improved by improving the snow performance, the actual contact area with the road surface (the area where the block surface and the road surface actually contact) is small. Therefore, there is a tendency that the adhesive frictional force of the entire tire is reduced and the performance on ice is deteriorated. As described above, there is a trade-off between performance on snow and performance on ice, and it has been difficult to improve the two in a well-balanced manner.

An object of the present invention is to provide a pneumatic tire which improves the performance on snow and the performance on ice in a well-balanced manner.

[0006]

In order to achieve the above object, a pneumatic tire of the present invention comprises a carcass folded around a bead core of a bead part from a tread part to a sidewall part and a radial direction of the carcass. A belt layer disposed outside and inside the tread portion. The tread portion extends in the tire circumferential direction and is divided into a tire equatorial side crown portion TC and an outer shoulder portion TS thereof. By providing a circumferential vertical groove including a pair of main vertical grooves and a lateral groove intersecting with the vertical groove, a block pattern is formed in the tread portion, while the tire is assembled on a regular rim and the regular internal pressure is filled. In a normal internal pressure state, the tread width TW of the tread portion is 0.75 to 0.85 times the tire cross-sectional width W, and the belt maximum width BW of the belt layer is the tread width. 0.7 to 0.8 times the head width TW,
The crown width TWC of the crown portion TC is 0.4 to 0.6 times the tread width TW, the radius of curvature TR1 of the crown portion TC is 2.7 to 3.1 times the tread width TW,
Moreover, the radius of curvature TR2 of the shoulder portion TS is set to be 2.2 to 2.6 times the tread width TW, and the crown portion is provided on the ground contact surface of the tread portion when a regular load is applied to the tire in the regular internal pressure state. Ratio AC / A between the total surface area AC of the block included in TC and the total area A of the ground plane
Is 0.3 to 0.45, and the ratio AS / A between the total surface area AS of the block included in the shoulder portion TS and the total area A of the ground contact surface is 0.2 to 0.3.

[0007]

By the main longitudinal groove in the tire circumferential direction, the tread surface is divided into a crown portion at the center of the tread having a width TWC of 0.4 to 0.6 times the tread width TW and a shoulder portion outside thereof. ing.

As a result of the research by the inventor, the crown portion and the shoulder portion have different contribution ratios relating to the snow performance and the ice performance, and as will be described later, when the actual ground contact area is constant, the crown portion It has been found that an increase in the ground contact pressure can improve the performance on ice while substantially maintaining the performance on snow, and a decrease in the ground contact pressure on the shoulder portion can improve the performance on snow while substantially maintaining the performance on ice.

Therefore, the double-crown radius in which the curvature radius TR1 of the crown portion is 2.7 to 3.1 times the tread width TW and the curvature radius TR2 of the shoulder portion is 2.2 to 2.6 times the tread width TW. By adopting, it is possible to form a tread profile in which the ground contact pressure of the crown part is large and the ground contact pressure of the shoulder part is small, and a high on-ice performance with a high contribution rate to the crown part and a high on-snow performance with a high contribution rate to the shoulder part, respectively. It can be shared and demonstrated.

Moreover, the ratio AC / A is set to 0.3 to 0.45, the ratio AS / A is set to 0.2 to 0.3, and the total surface area of the block at the ground contact surface is made large at the crown portion and small at the shoulder portion. Since they are distributed, the actual ground contact area at the crown portion increases, the total adhesive friction force can be further improved, and the performance on ice can be further enhanced. Further, the actual ground contact area at the shoulder portion is reduced, and the volume of the snow pillar that is set in the groove is increased, so that the performance on snow can be further improved.

Since the tread width TW is increased to 0.75 to 0.85 times the tire cross section width W, it is useful for increasing the ground contact width, that is, the entire ground contact area, and the belt width BW is 0.7 times the tread width TW. By restricting the contact radius to 0.8 times, it is possible to achieve the difference in the ground contact pressure due to the curvature radii TR1 and TR2.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridional section of a tire having a regular rim assembled to a regular rim and filled with a regular internal pressure. The pneumatic tire 1 has bead portions 3 on both sides through which a bead core 2 passes,
3, sidewall portions 4 extending outward from each bead portion 3 in the tire radial direction, and a tread portion 5 connecting between upper ends thereof.
In this example, which is provided with a tire size of 10.00R20, the tire is formed as a heavy-duty vehicle tire. In addition, a carcass 6 that folds around the bead core 2 from the tread portion 5 through the sidewall portion 4 is bridged between the bead portions 3 and 3, and the carcass 6 is radially outward and inside the tread portion 5. The tough belt layer 7 is wound.

The carcass 6 is a radial direction array using at least one carcass ply in which the carcass cords are arrayed at an angle of 75 to 90 degrees with respect to the tire equator CO. Other carcass cords include steel cords. Fiber cords such as nylon, polyester, and yon are used.

The belt layer 7 includes at least one belt ply 7A (fourth in this example, first and second from the carcass side) in which belt cords are arranged at an angle of 10 to 70 degrees with respect to the tire equator CO. Third and fourth belt plies 7A1, 7
A2, 7A3, 7A4), the belt cords of the first and second belt plies 7A1, 7A2 are in the same direction, and the belt cords of the third and fourth belt plies 7A3, 7A4 are in the same direction. Moreover, it intersects with the first and second belt cords. Further, as the belt cord of this example, a metal fiber cord such as steel is used, but other organic fiber cords such as nylon, polyester and rayon can also be used. In this example, the second belt ply 7A2 is the largest ply cord. Has a width.

As shown in FIG. 2, the tread surface S, which is the outer surface of the tread portion 5, is divided by a longitudinal groove G extending in the tire circumferential direction and a lateral groove Y in the direction intersecting with the longitudinal groove G. Block pattern is formed.

The vertical groove G includes a pair of, for example, zigzag-shaped main vertical grooves GO, GO arranged on both sides of the tire equator CO and having a groove width GW of 8 to 15 mm.
Have the same zigzag pitch and are arranged with a phase shift in the dividing direction of about 1/2 pitch, so that the main vertical groove GO is formed substantially line symmetrical with respect to the tire equator CO.

Further, the main vertical groove GO extends continuously in the tire circumferential direction, so that the tread surface S becomes a crown portion TC which includes the tire equator CO and is arranged between the main vertical grooves GO and GO. , Shoulders TS, TS on the outer side in the tire axial direction of the crown portion TC are divided into three regions.

The crown width TWC, which is the distance in the tire axial direction of the crown portion TC, is 0.4 to 0.6 times the tread width TW. Therefore, the shoulder width TWS of the remaining shoulder portion TS is the tread. The width TW is 0.
It is in the range of 3 to 0.2 times.

Further, the tread surface S is the crown portion TC.
Has a double crown radius whose outer surface is formed by a large arc having a curvature radius TR1 and the outer surface of the shoulder portion TS is formed by a small arc having a curvature radius TR2, and the tread surface S extends from the sidewall portion 4 in a concave arc buttress. Surface BS
It has a so-called square shoulder that intersects with the intersection angle.

Here, the radius of curvature TR1 is the tread width T.
It is necessary that 2.7 to 3.1 times W and the radius of curvature TR2 be 2.2 to 2.6 times the tread width TW. By setting TR1> TR2 in such a range, A profile in which the ground pressure at the crown portion TC is large and the ground pressure at the shoulder portion is small can be obtained.

By making the ground pressure different between the crown portion TC and the shoulder portion TS, it becomes possible to improve both the performance on ice and the performance on snow. This is based on the relationship between the ground contact pressures of the parts TC and TS found by the present inventor and the performance on ice and the performance on snow. This relationship is shown in FIGS. 3 (a) and 3 (b). That is, as shown in the figure,
When the actual ground contact area is constant, as the ground contact pressure of the crown portion TC increases, the performance on ice improves significantly, but the degree of improvement on snow performance is extremely low; and the shoulder portion TS.
It can be seen that as the ground contact pressure of No. 1 is reduced, the performance on snow is greatly improved, but the degree of deterioration on ice is extremely low. As described above, the contribution ratios of the ground pressures of the respective parts TC and TS to the performance on ice and the performance on snow are different from each other. As in the present application, the ground pressure of the crown part TC is made large and the ground pressure of the shoulder part TS is made small. By distributing, it is possible to maximize the above-mentioned characteristics and improve both the performance on snow and the performance on ice.

In order to surely distribute the ground pressure, the maximum belt width BW of the belt layer 7 which is the ply width of the second belt ply 7A2 is set to 0.7 to 0.8 of the tread width TW. It is necessary to double the length of the tread portion 5 and to reinforce it over the entire width of the tread portion 5 with a hoop effect. That is, when the maximum belt width BW is less than 0.7 TW, the hull effect is not sufficiently exerted in the shoulder portion TS, the profile is not maintained due to lifting or the like, and the shoulder rigidity becomes too small, resulting in insufficient cornering force. In addition, turning performance is impaired by sometimes inviting the person to sit down.
Conversely, if it exceeds 0.8 TW, the belt end and the buttress surface BS
And are close to each other and cause peeling of the belt end.

The tread width TW is about 0.7 times the tire sectional width W of a normal tire, whereas
The present invention is enhanced to 0.75 to 0.85 times. This helps to increase the ground contact width, that is, the entire ground contact area, a higher adhesive frictional force can be obtained, and the effect of improving the ice and snow performance by the distribution of the ground contact pressure can be further enhanced.

Block patterns having different actual contact areas are formed on the crown portion TC and the shoulder portion TS having different contact pressures.

That is, in this example, the crown portion TC has an inner sub-vertical groove G1 passing through the tire equator CO and an outer sub-vertical groove G2 extending between the sub-vertical groove G1 and the main longitudinal groove GO. , And a plurality of lateral grooves Y1 extending across the sub-vertical grooves G1 and G2 and extending between the main longitudinal grooves GO and GO, whereby the crown portion TC constitutes a block pattern having four block rows R1.

Zigzag grooves are used for the sub-vertical grooves G1 and G2 in this example, which has a narrower groove width than the main vertical groove GO. Further, each block B1 forming the block row R1 is formed with a siping 13 that extends between the block side walls in the tire axial direction and closes its opening at the time of contact with the ground, while maintaining the block rigidity to the ice road surface. Enhances the scratching effect of.

In the shoulder portion TS, the inner end communicates with the main vertical groove GO and the outer end has the buttress surface BS in this example.
A lateral Y-shaped lateral groove Y2 that opens at is provided, whereby the shoulder portion TS alternately includes an outer block B2 in contact with the tread edge e and an inner block B3 spaced inward from the tread edge e. The row of blocks R2 is formed.

The blocks B2 and B3 are also provided with sipings 14 and 15 extending in the tire axial direction, and the number, length and shape of the sipings 13 and 14 and 15 are determined according to the required tire performance. .

Further, in the present invention, the tire 1 in the normal internal pressure state is subjected to a total load of blocks included in the crown portion TC on the ground contact surface K where the tread surface S contacts the road surface under a normal load applied by JIS or the like. The ratio AC / A of the surface area AC to the total area A of the ground plane K is set to 0.3 to 0.45, and the ratio AS / A of the total block surface area AS included in the remaining two shoulder portions TS to the total area A. Is set to 0.2 to 0.3.

As described above, since the total surface area (AC + AS) of all blocks in the ground contact surface K is largely distributed by the crown portion TC which has a high contribution rate to the performance on ice, a large actual ground contact while maintaining a high ground contact pressure to some extent. Area is obtained, and as a result, higher adhesive frictional force can be generated to further improve the performance on ice. If the ratio AC / A exceeds 0.45, the ground pressure will be lowered, and the effect of distributing the ground pressure will be impaired, and the performance on ice will be lowered. Further, when the ratio AC / A is less than 0.3, the ground contact pressure becomes excessive, which causes melting of ice on the lower surface of the block, and similarly reduces the performance on ice.

In the shoulder portion TS having a high contribution rate to snow performance, since the block surface area is distributed to a small amount, the actual ground contact area can be reduced while maintaining a low ground contact pressure. As a result, it is possible to increase the volume of the snow pillar that is set in the groove and further improve the snow performance. The ratio AS / A
When the value is larger than 0.3, it is difficult to increase the groove volume, and when the value is smaller than 0.2, the ground pressure distribution effect is impaired such that the ground pressure is increased, and the snow performance is deteriorated.

[0032]

As described above, the pneumatic tire of the present invention employs a predetermined double crown radius to provide a difference in ground contact pressure between the crown portion and the shoulder portion which are divided by the main vertical groove, and the crown portion is different. Since the block surface area is distributed in a predetermined ratio to the shoulder portion and the shoulder portion, the performance on snow and the performance on ice of the tire as a whole are improved in a well-balanced manner.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a tire according to an embodiment of the present invention.

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

FIG. 3 is a diagram showing a relationship between a ground contact pressure of a crown portion and performance on snow and ice.

FIG. 3 is a diagram showing the relationship between the ground contact pressure of the shoulder portion b and the performance on snow and ice.

FIG. 4 is a diagram illustrating block traction on a snowy road.

FIG. 5 is a diagram illustrating an ice road surface scratching effect.

[Explanation of symbols]

 2 bead core 3 bead part 4 sidewall part 5 tread part 6 carcass 7 belt layer G vertical groove GO main vertical groove Y, Y1, Y2 horizontal grooves

Claims (1)

[Claims] 1. A tread comprising a carcass folded from a tread portion to a sidewall portion around a bead core of a bead portion, and a belt layer arranged radially outside the carcass and inside the tread portion. A circumferential vertical groove that includes a pair of main vertical grooves that divides the tread portion into a tire equatorial side crown portion TC and a shoulder outer portion shoulder portion TS that extends in the tire circumferential direction. While forming the block pattern in the tread portion by providing the intersecting lateral groove, the tread width TW of the tread portion is set to 0 of the tire cross-section width W in the normal internal pressure state in which the tire is assembled on the regular rim and the regular internal pressure is filled. .75 ~
0.85 times, the maximum belt width BW of the belt layer is 0.7 to 0.8 times the tread width TW, the crown portion T
The crown width TWC of C is 0.4 to 0.4 of the tread width TW.
0.6 times, the curvature radius TR1 of the crown portion TC is 2.7 to 3.1 times the tread width TW, and the curvature radius TR2 of the shoulder portion TS is 2.2 to the tread width TW.
In addition to 2.6 times, in the ground contact surface of the tread portion when a normal load is applied to the tire in the normal internal pressure state,
Total block surface area AC included in the crown portion TC
And the total area A of the ground plane AC / A is 0.3 to 0.4
5, and the ratio AS / A of the total surface area AS of the block included in the shoulder portion TS and the total area A of the ground contact surface is 0.2.
A pneumatic tire characterized by having a value of up to 0.3.