JPH0417803B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial application field The present invention can be installed on a passenger car etc. to exhibit excellent traction performance and braking performance on slippery snow-covered roads.
After the snow melts, the present invention relates to a tire whose tread pattern changes as it wears so that it exhibits excellent traction and braking performance on normal dry road surfaces and rainy road surfaces. (b) Prior Art As a mechanism for generating traction force or braking force between tires and the road surface under various road surface conditions, the following mechanism makes a large contribution. When a tire hits the snow on a snow-covered road, the tread surface of the tire sinks below the snow surface, first the concave part of the tread pattern is filled with snow, and then as the tire rotates,
As a result of the wall of the recess of the tread falling slightly forward or backward, the snow filled in the recess is compacted by the walls of the recess, and a reaction force is applied, generating traction or braking force. Therefore, in order to generate a large tractive force or braking force, it is preferable that the mass of snow that falls into the recesses of the tread pattern is larger, so a tire having a large number of large recesses of a certain depth is desirable. On the other hand, when it rains, the road surface is covered with a film of rainwater, and the tires float on the water film, making it difficult for braking force to act. When the ridges extending in the direction break the water film and temporarily store water in the recesses, and the tread surface directly contacts the road surface, braking force, etc. is generated. Therefore, on a rainy road surface, a treaded pattern with many ridges that break the water film is preferable. On the other hand, on a dry road surface, the frictional force acting between the road surface and the tread surface of the tire acts as a traction force, so the larger the area of the tread-patterned contact patch, the better. As described above, the conditions for the preferred tread pattern differ depending on the road surface condition. In order to use the same tires throughout each season in snowy areas, the tires must meet all of the above conditions. In order to satisfy the above conditions as much as possible, snow tires conventionally used in snowy areas are tires with a so-called block pattern, in which the land area of the tread is divided by a continuous network of grooves, and the land areas form mutually independent blocks. is used. (c) Problems to be solved by the invention In conventional block pattern tires, when trying to widen the groove width of the block pattern to increase the mass of snow filled in the grooves in order to increase the traction force during snowy conditions, block pattern tires Since the blocks are independent of each other, their rigidity is reduced, and when traction force is applied, the blocks cannot withstand the drag of compacted snow, and the blocks fall over, reducing the reaction force received from the road surface, and the tires On the contrary, the traction force will decline. Therefore, it is not possible to increase the area of the recessed portion filled with snow, and the ability to climb a slope on a snow-covered road surface is insufficient. In addition, when conventional block pattern tires are used on roads other than snow-covered roads, the actual ground contact area is small, so they wear out quickly, especially in the summer when the amount of wear per unit mileage is large, and their lifespan ends early. There were flaws. Therefore, in the present invention, even if the area of the concave portion of the tread is increased and the amount of snow filled into the concave portion is increased, the rigidity of the land portion of the tread pattern does not decrease, the traction force and braking force on snow-covered road surfaces are large, and the amount of snow is increased. To provide a snow tire capable of exerting large tractive force and braking force even after the land part of the tread wears out due to running on a rough road surface, has a long service life, and can be used in all seasons. (d) Means for Solving the Problems In order to achieve the above object, the inventors of the present invention have conducted repeated research and found that the unevenness of the conventional block pattern tire tread pattern has been reversed to create a continuous net-like land area. By providing mutually independent recesses surrounded by land parts, the land parts are continuous in a net shape, increasing its rigidity, so it is possible to increase the area of the recesses and increase the traction force on snow-covered roads. I found it. Furthermore, they discovered that by providing a groove on the bottom of the recess, when the land portion wears out and the bottom of the recess comes into contact with the ground, the groove acts as a tread groove, extending the life of the tire. It was completed. Next, the content of the present invention will be explained in detail with reference to the drawings. FIG. 1 is a developed view of the tread pattern of the tire of the present invention developed on a plane, and FIGS. 2 and 3 are cross-sectional views of the tire along lines AA and BB. In the drawing, a tread pattern 3 is provided on the tread surface 2 of the tread rubber 1, and the tread pattern 3 is composed of land portions 4 that are continuous in a net shape and polygonal recesses 5 surrounded by the land portions 4 and arranged in large numbers independently from each other. do. A groove 7 is provided in the bottom surface 6 of the recess 5. Groove 7 is oriented vertically, i.e. at the center line of the tire's tread.
II' parallel to or along the diagonal direction. Furthermore, it is preferable to provide the bottom surface 6 with a short support groove 8 branching from the groove 7 in a direction substantially perpendicular thereto. Land portion 4 within the tread width TW of the tread pattern 3
The surface area of , that is, the actual ground contact area is 20
~60% preferably 30-50%. Here, the tread width TW is the distance between the intersection points 10 and 10' of the circular arc connecting the surface of the tread pattern 3 and the extension line of the tread rubber side part 9 in the cross-sectional view of FIG. Width TW
and the circumferential length of the tire, and the surface area of the land portion 4 is determined as the remaining area obtained by subtracting the total area of the openings of the recesses 5 from the tread surface area. If the surface area of the land portion 4 is smaller than 20% of the tread surface area, wear will be rapid on a dry road surface, and traction force will be reduced on a snowy road surface. If it exceeds 60%, the amount of snow that fills the recesses will decrease and the traction force on snowy areas will decrease. The width of the land portion LW is set to 3 to 15% of the tread width TW.If the width of the land portion is smaller than 3% of the tread width, the rigidity of the land portion 4 will decrease and the traction force on snowy areas will decrease, resulting in a reduction of 15%. If the value exceeds 1, the concave portion 5 becomes smaller and the amount of snow that is filled in the concave portion and compacted becomes smaller, and the rigidity of the land portion 4 becomes too large and the amount of snow required to compact the snow filled in the concave portion 5 becomes too large.
Since the land portion 4 forming the side surface of the recess 5 does not move and the snow is not sufficiently compacted, the traction force becomes small. On the other hand, the width of the land portion 4 cannot be made larger than 15% of the tread width while keeping the surface area of the land portion 4 at 60% or less of the tread surface area. As shown in FIG. 2, the depth K of the recess 5 is 0.3 of the thickness T of the tread rubber 1 measured from the tread surface.
Make sure that the bottom surface 6 is within the range of ~0.5 times. If the bottom surface 6 is more than 0.3 times the thickness of the tread rubber, the thickness of the snow filling the recess 5 will be insufficient, resulting in a small traction force, and if it is more than 0.5 times the thickness, the wear life will be shortened. Furthermore, the depth M of the bottom of the groove 7 provided on the bottom surface 6 from the tread surface is such that the groove bottom 11 is 0.5 of the tread thickness.
Make it appear at ~0.9 times. If the groove bottom 11 is more than 0.5 times the tread thickness, the thickness of the tread rubber below the groove bottom 11 will increase, and when the tread rubber is driven for a long time at high speed in summer, heat will accumulate and the tread internal temperature will rise, causing the separation. If the groove bottom 11 is less than 0.9 times the tread thickness, the rubber of the groove bottom 11 becomes thinner and cracks easily occur in the groove bottom 11, and the belt cord becomes partially thick. Parts may be exposed. FIG. 3 shows a longitudinal cross-sectional view taken along line CC in FIG. 1. As shown in FIG. 3, on the bottom surface 6 of the recess,
It is preferable to provide horizontally shallow corrugated irregularities 12. Then, when you step on the snow surface and the recess 5 is filled with snow, some of the air in the recess 5 is compressed and accumulates in the corrugated irregularities 12, and when the tread surface separates from the road surface, The air accumulated in the concavities and convexities 12 expands and pushes out the snow filled in the concavities 5, and cooperates with the centrifugal force to enhance the effect of expelling snow from the concavities 5. When driving on a road surface with a water film formed by melting snow, if there are insufficient ridges of the tread pattern 3 to break the water film, microsipes 1 are added to the surface of the land portion 4 of the tread.
Arranging a large number of 3 in the width direction of the tread has the effect of breaking the water film. The depth S of the microsipes 13 is 0.1 to 0.3 times the thickness T of the tread. Furthermore, the fourth
As shown in the figure, a sipe 14 with a width of 1 mm or less is attached to the bottom of the recess 5 along the side wall of the recess 5 that is oriented at an angle of 50 to 90 degrees with respect to the tire circumferential direction.
When the net-like land portion 4 wears out and the bottom surface 6 of the recess 5 comes into contact with the ground, the sipe 1
The edges of the grooves 4 and 8 form an effective ridge for breaking the water film. FIG. 5 shows a developed view of the tread pattern of the ground contact portion of the tread of another embodiment of the tire. The recess 5 has a hexagonal planar shape, and the groove 7 on the bottom surface 6 of the recess 5
are provided obliquely with respect to the center line II' of the tread, and the lateral component length of the ridge of the groove 7 is large, so that when the land portion 4 is worn out and used as a summer tire, it breaks the water film on the road surface. This is preferable because the effect is greater. (e) Example Three types of radial tires of the present invention having a tire size of 165SR13 and having the tread patterns shown in FIGS. 1 and 5 were manufactured. The main constituent elements of the tread pattern are shown in Examples 1 to 3 in Table 1. Toledo

【table】

[Table] Values marked with ○ are outside the scope of the present invention.
Tires that were completely the same as those in Examples 1 to 3 were manufactured except for the main constituent elements, and these are similarly shown in Table 1 as Comparative Examples 1 to 8. Comparative Example 8 is a tire with a conventional block pattern. The tires of Examples 1 to 3 and Comparative Examples 1 to 8 were tested for hill climbing performance, drum durability, and wear, and the results are shown in Table 1. The hill-climbing performance was determined by installing the test tires on the drive shaft of the test vehicle, and measuring the slope by approximately 3 cm on the paved road surface.
The time required to travel 200 m on a slope covered with thick compacted snow was measured, and the reciprocal of the time and the evaluation score of the observed tire spinning condition were expressed as an index with the conventional tire (Comparative Example 8) set as 100. The drum durability test was conducted in accordance with the durability test specified for JIS D 4230 automobile tires. If you complete the specified conditions, it will last an additional 10 hours. What I was able to complete
100, and for those that fail during the process,
The distance traveled is expressed as an index. The test tire is mounted on a car and driven on a non-snow-covered road surface to determine the mileage per unit wear thickness of the tread pattern.Then, the mesh land area is ground away and the unit wear thickness of the groove pattern is determined. The mileage per hit was calculated and the wear life was estimated by multiplying by the thickness of each pattern. (f) Effects of the Invention According to the tire having the tread pattern of the present invention, since the land portion of the tread is continuous in a net shape, even if the area of the concave portion is increased, the rigidity of the land portion can be maintained high, and snow accumulation can be maintained. The mass of snow that fills the recesses on the road surface can be increased, and the large amount of packed and compacted snow and the rigidity of the net-like land portion increase the traction force and braking force on the snow-covered road surface. When driving on a snow-free road surface and the net-like land portion wears down and the bottom of the recess comes into contact with the ground, the grooves provided on the bottom of the recess act as normal tread grooves, increasing traction and braking force on wet roads. This is effective, extending the life of the tire. Furthermore, if a large number of microsipes are provided on the surface of the land portion almost along the width direction of the tire, the effect of breaking the water film when driving on a wet road surface during snow melting becomes greater, increasing the traction force and braking force.

[Brief explanation of drawings]

Fig. 1 is a developed view of the tread pattern of a tire having a tread pattern of the present invention, Figs. 2 and 3 are cross-sectional views of the same tire taken along lines AA and BB in Fig. 1, and Fig. 4 is a cross-sectional view taken along the line CC of the same tire. FIG. 5 is a developed view of the tread pattern of another embodiment of the present invention. 1... Treaded rubber, 2... Tread surface, 3... Treaded pattern, 4... Land part, 5... Recessed part, 6... Bottom surface, 7... Groove, 8... Support groove, 9... Treaded rubber side part, 10, 10'...intersection, 11...groove bottom, 1
2...Corrugated irregularities, 13...Microsipes, 1
4...Sipe.

Claims (1)

[Scope of Claims] 1. It has a continuous land portion in the form of a net and a large number of polygonal recesses arranged independently from each other surrounded by the land portion, and the bottom surface of the recess extends from the tread surface to the tread rubber. A tread pattern characterized by a groove located at a depth of 0.3 to 0.5 times the thickness of the tread rubber, and a groove having a depth from the tread surface to the groove bottom of the tread rubber of 0.5 to 0.9 times the thickness of the tread rubber. Tires with 2. A tire having a tread pattern according to claim 1, wherein the ratio of the surface area of the land portion to the tread surface area is 20 to 60%. 3. A tire having a tread pattern according to claim 2, wherein the ratio of the surface area of the land portion to the tread surface area is 30 to 50%. 4. A tire having a tread pattern according to claim 1, wherein the width of the land portion is 3 to 15% of the tread width. 5. On the surface of the land area, approximately along the width direction of the tire, a width of 0.5 mm or less and a depth of 0.1 to 0.1 to the thickness of the tread rubber.
A tire having a tread pattern according to claim 1, in which a large number of microsipes of 0.3 times the size are provided.